I just encountered this issue as well. I was running Unraid 6.8.2 for a long while - mounting NFS shares using fstab on Linux Mint 20, with no issues. I just updated to 6.8.3 and I'm experiencing the same behavior as everyone else. As soon as a file is written over a cache-enabled share, the share dies. Subsequent access attempts give me the "stale file handle" error. I tested a share with CIFS and it does the same thing.
Ultimately I disabled the cache on each share and it works like others have mentioned. It's far from an ideal solution though.