Thanks for the update. I wanted to share a quick note from my side. I tested the same workflow on InDesign version 21.1 and was able to open the cloud document, see the synced edits, and save it locally without running into the issue you described.
If you're able to, please try updating InDesign to the latest available 21.1 version and then test the workflow again.
Please let me know how it goes after the update. Looking forward to hearing back the observations.
Abhishek