Comment # 14 on bug 1163596 from Donald Curtis

It gets worse - Sunday afternoon backup to the QNAP NAS ��� NFS mount using IPv6
��� mount OK but, the rsync file transfers failed with a socket error and the
following in the systemd Journal entries:

M��r 08 16:11:23 xxxx kernel: nfs: RPC call returned error 95
M��r 08 16:11:24 xxxx kernel: nfs: RPC call returned error 95
M��r 08 16:11:24 xxxx kernel: nfs: RPC call returned error 95
M��r 08 16:11:25 xxxx kernel: nfs: RPC call returned error 95
M��r 08 16:11:27 xxxx kernel: nfs: RPC call returned error 95
M��r 08 16:11:31 xxxx kernel: nfs: RPC call returned error 95
 .
 .
 .

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Reverting to an IPv4 mount corrected the problem.