Only one job fails using same credentials

[itteam]

RESOLVED as I was typing the info here - posting anyway it case it helps anyone else...
But I'd also appreciate if someone can explain why this is.

Using HBS to rsync from a local NAS (buildingA) to a remote NAS (buildingB)
One job (of Public share) stopped working yesterday, the other 2 continue to work on schedule.
All 3 of these jobs use the same Storage Space Profile for the remote NAS

The error is
@ERROR: auth failed on module Public
[Hybrid Backup Sync] Failed to complete Sync job: "Public to XXX". Failed to authenticate credentials. Check username and password.

On the remote NAS, I can see the usual "Login OK" message at the scheduled time of the failed job and when I action [Sync Now] to attempt to get it to run manually. There is no error message on the remote NAS.

Another job from same source NAS (buildingA) to another NAS (same buildingA) for the Public share is running AOK, so we can rule out any issue with the folder permissions on the source NAS. Nothing at all had been changed on the remote NAS preceeding the failure.

ANSWER: "compress files during transmission" had been turned on yesterday only on the failing job. Disabling this 'Policy' choice fixed the issue.