Same for me, running UNRAID 6.9.0 and Ubuntu 20.04 in a VM.
I've mounted an UNRAID NFS export in the Ubuntu VM using the /etc/fstab file and the following configuration:
10.10.xxx.yyy:/mnt/user/share /mnt/share nfs rw 0 0
Randomly after some time (sometimes after minutes or sometimes after hours) the NFS export is not accessible anymore. When I try to view the mounted content by typing "ls /mnt/share", I get the following error: "ls: cannot access '/mnt/share': Stale file handle"
Already disabled "Tunable (support Hard Links)" in "Global Share Settings". Also disabled caching for this particular share where I have got the issue.
Anyone find a solution or workaround for this issue already?