Cannot save odt due to sub-document content.xml

Hi All. I cannot save an odt file with error writing sub-document content.xml. It worked the last time I tried which was a month ago. I can save it as a docx file, open that and then I can save it as an odt. I am using 7.1.3.2 on Fedora 34. Seems to be something that has popped up before in the bug list. Thanks