Several days ago my SimpleShare desktop NAS stopped responding via NFS. Access to the web interface was still functional with no errors, a cursory disk check found no problems, rebooting the drive didn’t fix it. However, attempting to mount the drive over CIFS (samba) worked. After that NFS access worked again, for whatever reason. For other unknown reasons, fixing this problem also fixed an annoying hang on shutdown that happened at the “Unmounting all filesystems” step. How a problem with a NFS share could cause this I don’t know.