Thsi build has a bug which makes the rwdata partition to become full. But that does not explain the issues you are having exactly.
So I’m more inclined to think the APIM has gone bad.
You could try troubleshooting the bug by following this guide → APIM Sync Settings Not Saving, VER_ERR08 Errors, Cannot Perform Master Reset or Upgrades/Updates (Solved)
But, again, the rwdata partition being full would not explain the issues you are seeing.