The fix for this issue is now available in the latest update of InDesign – that is, InDesign 15.0.2.
Please update your InDesign application to get this fix.
Adobe InDesign team
An error occurred while saving the commentMary commented
Having the same problem as well. I work for a huge company that pays for cloud. This is very unprofessional that I can't save or undo.
WORKAROUND: Export as an IDML and open it that way. Test it before you open your original file. This has happened to me with two different files now