Error nfs_serverfault

The server hit an internal error

The NFS server itself failed while handling the request. Usually transient; if it repeats, the NAS's own log says why.

What this means

Status 10006, SERVERFAULT. Not a permissions or network problem — the server’s NFS daemon encountered an error it couldn’t classify.

What to do

1. Retry. Often it’s a momentary condition (a background scrub, a snapshot being taken).
2. Check the NAS log — Synology Log Center, QNAP System Logs, TrueNAS Alerts, journalctl -u nfs-server on Linux.
3. Storage — a dataset that’s locked, unmounted or degraded produces this on some servers rather than an I/O error.