Cannot delete archive or backups from it, getting "Failed to connect to service 'ASN'. Destination host unreachable

Trying to write to or delete backups from one specific archive (or the entire archive itself), task fails with this error:

Error code: 17
Module: 173
LineInfo: 1c13eceb383289b2
Fields: ServiceID : 34, $module : mms_vs_43956
Message: Failed to connect to service 'ASN'. Destination host 'backupadmin*****' is unreachable or a firewall may be blocking the connection.
--------------------

Backupadmin is the name of Acronis AMS.

Setup: the server that's being backed up is called QA. It's being backed to NAS1 and NAS2. At some point Acronis started failing the backup tasks with the above error when trying to write to NAS1 (NAS2 writes no problem). This archive only. The vault on NAS1 where QA archive resides has 9 other archives that are being used no problem.
I am RDP to the AMS server. I can connect to/from QA, to/from both NAS storages, all credentials are there, nothing changed, everything used to work fine before. We have Kaspersky, but I killed it both on AMS and QA with same results.

NAS2 - backups are accessible, writable, "deletable"
NAS1 - other 9 archives within the vault work fine. Just this 1 archive I cannot write to nor delete.

Just patched to latest. Issue remains.
Any ideas? Appreciate.