diff --git a/.github/workflows/test-stack-reusable-workflow.yml b/.github/workflows/test-stack-reusable-workflow.yml
index c5b1af959..050c6d61f 100644
--- a/.github/workflows/test-stack-reusable-workflow.yml
+++ b/.github/workflows/test-stack-reusable-workflow.yml
@@ -71,6 +71,7 @@ jobs:
           docker run test-changedetectionio  bash -c 'python3 -m unittest changedetectionio.tests.unit.test_watch_model'
           docker run test-changedetectionio  bash -c 'python3 -m unittest changedetectionio.tests.unit.test_jinja2_security'
           docker run test-changedetectionio  bash -c 'python3 -m unittest changedetectionio.tests.unit.test_semver'
+          docker run test-changedetectionio  bash -c 'python3 -m unittest changedetectionio.tests.unit.test_update_watch_deep_merge'
 
       - name: Test built container with Pytest (generally as requests/plaintext fetching)
         run: |
diff --git a/changedetectionio/blueprint/ui/__init__.py b/changedetectionio/blueprint/ui/__init__.py
index ce4bb716a..8f924cc08 100644
--- a/changedetectionio/blueprint/ui/__init__.py
+++ b/changedetectionio/blueprint/ui/__init__.py
@@ -303,7 +303,7 @@ def construct_blueprint(datastore: ChangeDetectionStore, update_q, worker_handle
         watch['ignore_text'] += datastore.data['settings']['application']['global_ignore_text']
         watch['subtractive_selectors'] += datastore.data['settings']['application']['global_subtractive_selectors']
 
-        watch_json = json.dumps(watch)
+        watch_json = json.dumps(dict(watch))
 
         try:
             r = requests.request(method="POST",
diff --git a/changedetectionio/model/Watch.py b/changedetectionio/model/Watch.py
index c2a8b9f57..3410e7979 100644
--- a/changedetectionio/model/Watch.py
+++ b/changedetectionio/model/Watch.py
@@ -43,14 +43,14 @@ class model(watch_base):
         self.__datastore_path = kw.get('datastore_path')
         if kw.get('datastore_path'):
             del kw['datastore_path']
-            
+        
+        # Save default before passing to parent, since parent will delete it
+        default_values = kw.get('default')
+        
         super(model, self).__init__(*arg, **kw)
-        if kw.get('default'):
-            self.update(kw['default'])
-            del kw['default']
-
-        if self.get('default'):
-            del self['default']
+        
+        if default_values:
+            self.update(default_values)
 
         # Be sure the cached timestamp is ready
         bump = self.history
@@ -227,8 +227,8 @@ class model(watch_base):
 
     @property
     def has_history(self):
-        fname = os.path.join(self.watch_data_dir, "history.txt")
-        return os.path.isfile(fname)
+        fname = self._get_data_file_path("history.txt")
+        return fname and os.path.isfile(fname)
 
     @property
     def has_browser_steps(self):
@@ -405,16 +405,16 @@ class model(watch_base):
         return not local_lines.issubset(existing_history)
 
     def get_screenshot(self):
-        fname = os.path.join(self.watch_data_dir, "last-screenshot.png")
-        if os.path.isfile(fname):
+        fname = self._get_data_file_path("last-screenshot.png")
+        if fname and os.path.isfile(fname):
             return fname
 
         # False is not an option for AppRise, must be type None
         return None
 
     def __get_file_ctime(self, filename):
-        fname = os.path.join(self.watch_data_dir, filename)
-        if os.path.isfile(fname):
+        fname = self._get_data_file_path(filename)
+        if fname and os.path.isfile(fname):
             return int(os.path.getmtime(fname))
         return False
 
@@ -441,20 +441,28 @@ class model(watch_base):
     @property
     def watch_data_dir(self):
         # The base dir of the watch data
-        return os.path.join(self.__datastore_path, self['uuid']) if self.__datastore_path else None
+        if self.__datastore_path and self.get('uuid'):
+            return os.path.join(self.__datastore_path, self['uuid'])
+        return None
+
+    def _get_data_file_path(self, filename):
+        """Safely get the full path to a data file, returns None if watch_data_dir is None"""
+        if self.watch_data_dir:
+            return os.path.join(self.watch_data_dir, filename)
+        return None
 
     def get_error_text(self):
         """Return the text saved from a previous request that resulted in a non-200 error"""
-        fname = os.path.join(self.watch_data_dir, "last-error.txt")
-        if os.path.isfile(fname):
+        fname = self._get_data_file_path("last-error.txt")
+        if fname and os.path.isfile(fname):
             with open(fname, 'r') as f:
                 return f.read()
         return False
 
     def get_error_snapshot(self):
         """Return path to the screenshot that resulted in a non-200 error"""
-        fname = os.path.join(self.watch_data_dir, "last-error-screenshot.png")
-        if os.path.isfile(fname):
+        fname = self._get_data_file_path("last-error-screenshot.png")
+        if fname and os.path.isfile(fname):
             return fname
         return False
 
diff --git a/changedetectionio/model/__init__.py b/changedetectionio/model/__init__.py
index 2a6587aa2..d857fdf40 100644
--- a/changedetectionio/model/__init__.py
+++ b/changedetectionio/model/__init__.py
@@ -1,13 +1,14 @@
 import os
 import uuid
+import json
 
 from changedetectionio import strtobool
 default_notification_format_for_watch = 'System default'
 
-class watch_base(dict):
+class watch_base:
 
     def __init__(self, *arg, **kw):
-        self.update({
+        self.__data = {
             # Custom notification content
             # Re #110, so then if this is set to None, we know to use the default value instead
             # Requires setting to None on submit if it's the same as the default
@@ -128,9 +129,78 @@ class watch_base(dict):
             'uuid': str(uuid.uuid4()),
             'webdriver_delay': None,
             'webdriver_js_execute_code': None,  # Run before change-detection
-        })
+        }
+        
+        if len(arg) == 1 and (isinstance(arg[0], dict) or hasattr(arg[0], 'keys')):
+            self.__data.update(arg[0])
+        if kw:
+            self.__data.update(kw)
 
-        super(watch_base, self).__init__(*arg, **kw)
+        if self.__data.get('default'):
+            del self.__data['default']
 
-        if self.get('default'):
-            del self['default']
\ No newline at end of file
+    def __getitem__(self, key):
+        return self.__data[key]
+
+    def __setitem__(self, key, value):
+        self.__data[key] = value
+
+    def __delitem__(self, key):
+        del self.__data[key]
+
+    def __iter__(self):
+        return iter(self.__data)
+
+    def __len__(self):
+        return len(self.__data)
+
+    def __contains__(self, key):
+        return key in self.__data
+
+    def __repr__(self):
+        return repr(self.__data)
+
+    def __str__(self):
+        return str(self.__data)
+
+    def keys(self):
+        return self.__data.keys()
+
+    def values(self):
+        return self.__data.values()
+
+    def items(self):
+        return self.__data.items()
+
+    def get(self, key, default=None):
+        return self.__data.get(key, default)
+
+    def pop(self, key, *args):
+        return self.__data.pop(key, *args)
+
+    def popitem(self):
+        return self.__data.popitem()
+
+    def clear(self):
+        self.__data.clear()
+
+    def update(self, *args, **kwargs):
+        self.__data.update(*args, **kwargs)
+
+    def setdefault(self, key, default=None):
+        return self.__data.setdefault(key, default)
+
+    def copy(self):
+        return self.__data.copy()
+
+    def __deepcopy__(self, memo):
+        from copy import deepcopy
+        new_instance = self.__class__()
+        new_instance.__data = deepcopy(self.__data, memo)
+        return new_instance
+
+    def __reduce__(self):
+        return (self.__class__, (self.__data,))
+
+    def to_dict(self):
+        return dict(self.__data)
\ No newline at end of file
diff --git a/changedetectionio/processors/restock_diff/__init__.py b/changedetectionio/processors/restock_diff/__init__.py
index 3d472beec..fe25a7a9c 100644
--- a/changedetectionio/processors/restock_diff/__init__.py
+++ b/changedetectionio/processors/restock_diff/__init__.py
@@ -42,10 +42,10 @@ class Restock(dict):
 
         # Update with any provided positional arguments (dictionaries)
         if args:
-            if len(args) == 1 and isinstance(args[0], dict):
+            if len(args) == 1 and (isinstance(args[0], dict) or hasattr(args[0], 'keys')):
                 self.update(args[0])
             else:
-                raise ValueError("Only one positional argument of type 'dict' is allowed")
+                raise ValueError("Only one positional argument of type 'dict' or dict-like is allowed")
 
     def __setitem__(self, key, value):
         # Custom logic to handle setting price and original_price
diff --git a/changedetectionio/store.py b/changedetectionio/store.py
index a7b7d809f..f1db296ec 100644
--- a/changedetectionio/store.py
+++ b/changedetectionio/store.py
@@ -23,6 +23,13 @@ from blinker import signal
 from .processors import get_custom_watch_obj_for_processor
 from .processors.restock_diff import Restock
 
+class WatchEncoder(json.JSONEncoder):
+    def default(self, obj):
+        from .model import watch_base
+        if isinstance(obj, watch_base):
+            return dict(obj)
+        return super().default(obj)
+
 # Because the server will run as a daemon and wont know the URL for notification links when firing off a notification
 BASE_URL_NOT_SET_TEXT = '("Base URL" not set - see settings - notifications)'
 
@@ -51,9 +58,6 @@ class ChangeDetectionStore:
         self.needs_write = False
         self.start_time = time.time()
         self.stop_thread = False
-        # Base definition for all watchers
-        # deepcopy part of #569 - not sure why its needed exactly
-        self.generic_definition = deepcopy(Watch.model(datastore_path = datastore_path, default={}))
 
         if path.isfile('changedetectionio/source.txt'):
             with open('changedetectionio/source.txt') as f:
@@ -174,6 +178,14 @@ class ChangeDetectionStore:
         self.__data['settings']['application']['password'] = False
         self.needs_write = True
 
+    def _deep_merge(self, target, source):
+        """Recursively merge source dict into target dict"""
+        for key, value in source.items():
+            if key in target and isinstance(target[key], dict) and isinstance(value, dict):
+                self._deep_merge(target[key], value)
+            else:
+                target[key] = value
+
     def update_watch(self, uuid, update_obj):
 
         # It's possible that the watch could be deleted before update
@@ -181,15 +193,8 @@ class ChangeDetectionStore:
             return
 
         with self.lock:
-
-            # In python 3.9 we have the |= dict operator, but that still will lose data on nested structures...
-            for dict_key, d in self.generic_definition.items():
-                if isinstance(d, dict):
-                    if update_obj is not None and dict_key in update_obj:
-                        self.__data['watching'][uuid][dict_key].update(update_obj[dict_key])
-                        del (update_obj[dict_key])
-
-            self.__data['watching'][uuid].update(update_obj)
+            # Use recursive merge to handle nested dictionaries properly
+            self._deep_merge(self.__data['watching'][uuid], update_obj)
         self.needs_write = True
 
     @property
@@ -393,6 +398,51 @@ class ChangeDetectionStore:
 
         return False
 
+    import json
+    import os
+    import tempfile
+    from pathlib import Path  # just for nicer paths
+
+    JSON_INDENT = 2  # or None in production
+    ENCODER = WatchEncoder  # your custom encoder
+
+    def save_json_atomic(self, save_path: str | os.PathLike, data) -> None:
+        """
+        Atomically (re)write *path* with *data* encoded as JSON.
+        The original file is left untouched if anything fails.
+        """
+        import tempfile
+        from pathlib import Path  # just for nicer paths
+
+        JSON_INDENT = 2  # or None in production
+        ENCODER = WatchEncoder  # your custom encoder
+
+        datapath = Path(save_path)
+        directory = datapath.parent
+
+        # 1. create a unique temp file in the same directory
+        fd, tmp_name = tempfile.mkstemp(
+            dir=directory,
+            prefix=f"{datapath.name}.",
+            suffix=".tmp",
+        )
+        try:
+            with os.fdopen(fd, "w", encoding="utf-8") as tmp:
+                json.dump(data, tmp, indent=JSON_INDENT, cls=ENCODER)
+                if os.getenv('JSON_SAVE_FORCE_FLUSH'):
+                    tmp.flush()  # push Python buffers
+                    os.fsync(tmp.fileno())  # force kernel to write to disk
+            os.replace(tmp_name, datapath)
+
+        except Exception as e:
+            logger.critical(f"Failed to write JSON to {datapath} - {str(e)}")
+            # if anything above blew up, ensure we don't leave junk lying around
+            try:
+                os.unlink(tmp_name)
+            finally:
+                raise
+
+
     def sync_to_json(self):
         logger.info("Saving JSON..")
         try:
@@ -404,18 +454,7 @@ class ChangeDetectionStore:
             self.sync_to_json()
             return
         else:
-
-            try:
-                # Re #286  - First write to a temp file, then confirm it looks OK and rename it
-                # This is a fairly basic strategy to deal with the case that the file is corrupted,
-                # system was out of memory, out of RAM etc
-                with open(self.json_store_path+".tmp", 'w') as json_file:
-                    # Use compact JSON in production for better performance
-                    json.dump(data, json_file, indent=2)
-                    os.replace(self.json_store_path+".tmp", self.json_store_path)
-            except Exception as e:
-                logger.error(f"Error writing JSON!! (Main JSON file save was skipped) : {str(e)}")
-
+            self.save_json_atomic(save_path = self.json_store_path, data =data)
             self.needs_write = False
             self.needs_write_urgent = False
 
diff --git a/changedetectionio/tests/unit/test_update_watch_deep_merge.py b/changedetectionio/tests/unit/test_update_watch_deep_merge.py
new file mode 100644
index 000000000..027aa4322
--- /dev/null
+++ b/changedetectionio/tests/unit/test_update_watch_deep_merge.py
@@ -0,0 +1,291 @@
+#!/usr/bin/env python3
+
+# run from dir above changedetectionio/ dir
+# python3 -m unittest changedetectionio.tests.unit.test_update_watch_deep_merge
+
+import unittest
+import os
+import tempfile
+import shutil
+from unittest.mock import patch
+
+from changedetectionio import store
+
+
+class TestUpdateWatchDeepMerge(unittest.TestCase):
+
+    def setUp(self):
+        # Create a temporary directory for test data
+        self.test_datastore_path = tempfile.mkdtemp()
+        self.datastore = store.ChangeDetectionStore(datastore_path=self.test_datastore_path, include_default_watches=False)
+        
+        # Create a test watch with known nested structure
+        self.test_uuid = self.datastore.add_watch(url='http://example.com')
+        
+        # Set up known initial nested structure
+        initial_data = {
+            'time_between_check': {'weeks': None, 'days': 1, 'hours': 6, 'minutes': 30, 'seconds': None},
+            'headers': {'user-agent': 'test-browser', 'accept': 'text/html'},
+            'time_schedule_limit': {
+                'enabled': True,
+                'monday': {
+                    'enabled': True,
+                    'start_time': '09:00',
+                    'duration': {'hours': '8', 'minutes': '00'}
+                },
+                'tuesday': {
+                    'enabled': False,
+                    'start_time': '10:00',
+                    'duration': {'hours': '6', 'minutes': '30'}
+                }
+            }
+        }
+        self.datastore.update_watch(self.test_uuid, initial_data)
+
+    def tearDown(self):
+        self.datastore.stop_thread = True
+        # Clean up the temporary directory
+        shutil.rmtree(self.test_datastore_path, ignore_errors=True)
+
+    def test_simple_flat_update(self):
+        """Test that simple flat updates work as before"""
+        update_obj = {'url': 'http://newexample.com', 'paused': True}
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        self.assertEqual(watch['url'], 'http://newexample.com')
+        self.assertEqual(watch['paused'], True)
+
+    def test_time_between_check_partial_update(self):
+        """Test partial update of time_between_check preserves existing keys"""
+        # Update only hours, should preserve other existing values
+        update_obj = {'time_between_check': {'hours': 2}}
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        time_check = watch['time_between_check']
+        
+        # Updated value
+        self.assertEqual(time_check['hours'], 2)
+        # Preserved existing values
+        self.assertEqual(time_check['days'], 1)
+        self.assertEqual(time_check['minutes'], 30)
+        self.assertEqual(time_check['weeks'], None)
+        self.assertEqual(time_check['seconds'], None)
+
+    def test_time_between_check_multiple_partial_updates(self):
+        """Test multiple partial updates to time_between_check"""
+        # First update
+        update_obj1 = {'time_between_check': {'minutes': 45}}
+        self.datastore.update_watch(self.test_uuid, update_obj1)
+        
+        # Second update
+        update_obj2 = {'time_between_check': {'seconds': 15}}
+        self.datastore.update_watch(self.test_uuid, update_obj2)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        time_check = watch['time_between_check']
+        
+        # Both updates should be preserved
+        self.assertEqual(time_check['minutes'], 45)
+        self.assertEqual(time_check['seconds'], 15)
+        # Original values should be preserved
+        self.assertEqual(time_check['days'], 1)
+        self.assertEqual(time_check['hours'], 6)
+
+    def test_headers_partial_update(self):
+        """Test partial update of headers preserves existing headers"""
+        update_obj = {'headers': {'authorization': 'Bearer token123'}}
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        headers = watch['headers']
+        
+        # New header added
+        self.assertEqual(headers['authorization'], 'Bearer token123')
+        # Existing headers preserved
+        self.assertEqual(headers['user-agent'], 'test-browser')
+        self.assertEqual(headers['accept'], 'text/html')
+
+    def test_headers_update_existing_key(self):
+        """Test updating an existing header key"""
+        update_obj = {'headers': {'user-agent': 'new-browser'}}
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        headers = watch['headers']
+        
+        # Updated existing header
+        self.assertEqual(headers['user-agent'], 'new-browser')
+        # Other headers preserved
+        self.assertEqual(headers['accept'], 'text/html')
+
+    def test_time_schedule_limit_deep_nested_update(self):
+        """Test deep nested update of time_schedule_limit structure"""
+        update_obj = {
+            'time_schedule_limit': {
+                'monday': {
+                    'duration': {'hours': '10'}  # Only update hours, preserve minutes
+                }
+            }
+        }
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        schedule = watch['time_schedule_limit']
+        
+        # Deep nested update applied
+        self.assertEqual(schedule['monday']['duration']['hours'], '10')
+        # Existing nested values preserved
+        self.assertEqual(schedule['monday']['duration']['minutes'], '00')
+        self.assertEqual(schedule['monday']['start_time'], '09:00')
+        self.assertEqual(schedule['monday']['enabled'], True)
+        # Other days preserved
+        self.assertEqual(schedule['tuesday']['enabled'], False)
+        self.assertEqual(schedule['enabled'], True)
+
+    def test_mixed_flat_and_nested_update(self):
+        """Test update with both flat and nested properties"""
+        update_obj = {
+            'url': 'http://mixed-update.com',
+            'paused': False,
+            'time_between_check': {'days': 2, 'minutes': 15},
+            'headers': {'cookie': 'session=abc123'}
+        }
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        
+        # Flat updates
+        self.assertEqual(watch['url'], 'http://mixed-update.com')
+        self.assertEqual(watch['paused'], False)
+        
+        # Nested updates
+        time_check = watch['time_between_check']
+        self.assertEqual(time_check['days'], 2)
+        self.assertEqual(time_check['minutes'], 15)
+        self.assertEqual(time_check['hours'], 6)  # preserved
+        
+        headers = watch['headers']
+        self.assertEqual(headers['cookie'], 'session=abc123')
+        self.assertEqual(headers['user-agent'], 'test-browser')  # preserved
+
+    def test_overwrite_nested_with_flat(self):
+        """Test that providing a non-dict value overwrites the entire nested structure"""
+        update_obj = {'time_between_check': 'invalid_value'}
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        # Should completely replace the nested dict with the string
+        self.assertEqual(watch['time_between_check'], 'invalid_value')
+
+    def test_add_new_nested_structure(self):
+        """Test adding a completely new nested dictionary"""
+        update_obj = {
+            'custom_config': {
+                'option1': 'value1',
+                'nested': {
+                    'suboption': 'subvalue'
+                }
+            }
+        }
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        self.assertEqual(watch['custom_config']['option1'], 'value1')
+        self.assertEqual(watch['custom_config']['nested']['suboption'], 'subvalue')
+
+    def test_empty_dict_update(self):
+        """Test updating with empty dictionaries"""
+        update_obj = {'headers': {}}
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        # Empty dict should preserve existing headers (no keys to merge)
+        self.assertEqual(watch['headers']['user-agent'], 'test-browser')
+        self.assertEqual(watch['headers']['accept'], 'text/html')
+
+    def test_none_values_in_nested_update(self):
+        """Test handling None values in nested updates"""
+        update_obj = {
+            'time_between_check': {
+                'hours': None,
+                'days': 3
+            }
+        }
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        time_check = watch['time_between_check']
+        
+        self.assertEqual(time_check['hours'], None)
+        self.assertEqual(time_check['days'], 3)
+        self.assertEqual(time_check['minutes'], 30)  # preserved
+
+    def test_real_world_api_update_scenario(self):
+        """Test a real-world API update scenario from the codebase analysis"""
+        # Based on actual API call patterns found in the codebase
+        update_obj = {
+            "title": "Updated API Watch",
+            'time_between_check': {'minutes': 60},
+            'headers': {'authorization': 'Bearer api-token', 'user-agent': 'api-client'},
+            'notification_urls': ['https://webhook.example.com']
+        }
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        
+        # Verify all updates
+        self.assertEqual(watch['title'], 'Updated API Watch')
+        self.assertEqual(watch['time_between_check']['minutes'], 60)
+        self.assertEqual(watch['time_between_check']['days'], 1)  # preserved
+        self.assertEqual(watch['headers']['authorization'], 'Bearer api-token')
+        self.assertEqual(watch['headers']['user-agent'], 'api-client')  # overwrote existing
+        self.assertEqual(watch['headers']['accept'], 'text/html')  # preserved
+        self.assertEqual(watch['notification_urls'], ['https://webhook.example.com'])
+
+    def test_watch_not_found(self):
+        """Test update_watch with non-existent UUID"""
+        # Should not raise an error, just return silently
+        fake_uuid = 'non-existent-uuid'
+        update_obj = {'url': 'http://should-not-update.com'}
+        
+        # Should not raise an exception
+        self.datastore.update_watch(fake_uuid, update_obj)
+        
+        # Verify no changes were made to existing watch
+        watch = self.datastore.data['watching'][self.test_uuid]
+        self.assertNotEqual(watch['url'], 'http://should-not-update.com')
+
+    def test_processor_style_update(self):
+        """Test the type of updates made by processors during check operations"""
+        # Based on async_update_worker.py patterns
+        update_obj = {
+            'last_notification_error': False,
+            'last_error': False,
+            'previous_md5': 'abc123def456',
+            'content-type': 'application/json',
+            'consecutive_filter_failures': 0,
+            'fetch_time': 1.234,
+            'check_count': 42
+        }
+        self.datastore.update_watch(self.test_uuid, update_obj)
+        
+        watch = self.datastore.data['watching'][self.test_uuid]
+        
+        # Verify processor updates
+        self.assertEqual(watch['last_notification_error'], False)
+        self.assertEqual(watch['last_error'], False)
+        self.assertEqual(watch['previous_md5'], 'abc123def456')
+        self.assertEqual(watch['content-type'], 'application/json')
+        self.assertEqual(watch['consecutive_filter_failures'], 0)
+        self.assertEqual(watch['fetch_time'], 1.234)
+        self.assertEqual(watch['check_count'], 42)
+        
+        # Verify nested structures weren't affected
+        self.assertEqual(watch['time_between_check']['days'], 1)
+        self.assertEqual(watch['headers']['user-agent'], 'test-browser')
+
+
+if __name__ == '__main__':
+    unittest.main()
\ No newline at end of file