The issue has been fixed in the latest release of InDesign – InDesign 2021.
Please update to this new version of InDesign to get the fix.
Adobe InDesign team
An error occurred while saving the commentLewis Crawford commented
I have the same issue and it only seems to be happening on my PC. My mac works fine. I was hoping the latest update would fix it but to no avail. I teach InDesign at my university and this has become an issue with online teaching. Most of my students have a PC and they are reporting the same error.