The fix for this issue is now available in the latest update of InDesign – version 16.1
Please update to this version to get the fix.
Adobe InDesign team
An error occurred while saving the commentAnonymous commented
I just had this same issue. Someone recommended deleting the fonts folder in the Collect For Output folder of your document. I did that, opened the file and it worked perfectly. Great save as I have 35 brochures designed with Avenir as the main font.
Mac OS Mojave