Save stops working, save as gives error message
After a period of time, save stops working. But it doesn't tell you that it has stopped working.
The save entry under the hamburger button is disabled (so it looks like save worked). However if you look at the save history (via the drop down centre top on the document name), it shows that the last save was way past any recent changes.
I have tested making changes and save still is disabled, and no auto saving is performed.
If I try saving as a new name (either locally or via the cloud), then the following error message is displayed:

My environment is:
- Windows 10 Pro Version 1903 OS build 18362.959
- Xd Version 32.0.22.11, Creative Cloud Sync 4.3.57.2
Note: searched on here and via google, couldn't find any info on this error or this problem.
