The ODF validator complains about an invalid attribute
style:contextual-spacing in styles.xml, ultimately an implementation
error in whatever old version of LibreOffice that produced the
data/odt/styles.xml (should have put it into an extension namespace).
Fortunately the attribute was added to ODF 1.3, which was released a
couple years ago.
So the easiest fix is to simply produce ODF 1.3 instead of 1.2; it's
supposed to be fully backward compatible.
Michael Stahl