FWIW: The latest release available on Amazon is 5.2.4.4. It has been there since 5/Feb so I don't know why you haven't seen it.
Nope, not a known problem. There haven't been any changes in the cloud code in months and Onedrive works for me.
You don't mention whether you are using an SD card. If so then you might be running into a rare problem where CC loses the privileges to write the app-private folder on the SD card. This shows up as an unexpected write error when saving the calibre database fetched from the cloud. We have seen this happen after OS (Android) upgrades.
You can tell CC not to store the cloud db on the SD card by going ot Settings / Connecting to calibre / Cloud Connection then checking the box "Save cloud cache in main memory". It things now work then we know that something has gone wrong with the SD card. If you aren't seeing any other problems then you might want to stick with this fix.
If you don't want to ignore it then sometimes uninstalling and reinstalling CC fixes it. Be sure to follow the steps in the FAQ
[Android] How do I reinstall CC without losing all my book information? so you don't need to resend all the books.