TS5400 Backup Error - Code 1

[CC99]

I have 3 TS5400s, one of which is a Backup Server. The other 2 have been backing up pretty much flawlessly for several year. The other night one of the backups failed.

-------- BEGIN BACKUP 2020/08/17 01:00:22 NAS03@array1/Share -> NAS05@array1/Backups-Auto-NAS03 --------
ERROR: failed to read a password from /tmp/rspasswd_4841
rsync error: syntax or usage error (code 1) at authenticate.c(212) [sender=3.1.0]
Can't write to backup destination(target disk is broken?).

Any ideas?

Thanks for any feedback!

CC