Have you had a look at the 2 TNs in Bill's post?
Important to change NBU services to domain logon account with write permissions on the CIFS share.
Extract from NBU Admin Guide I:
Configuring credentials for CIFS and disk storage units
ForCommonInternet File System (CIFS) storage with AdvancedDisk and BasicDisk
storage units, two NetBackup services on Windows computers require matching
credentials.
The following NetBackup services on Windows media servers to which the CIFS
storage is attached must use the same credentials:
■ NetBackup Client Service
The NetBackup Client Service is either bpcd.exe or bpinetd.exe, depending
on NetBackup release level. Regardless of the binary file name, the service
requires the credentials.
■ NetBackup Remote Manager and Monitor Service
The NetBackup Remote Manager and Monitor Service binary file name is
nbrmms.exe.
The credentials must be valid Windows credentials that allow read and write
access to the storage. Configure the credentials on the media server or media
servers that have a file system mount on the CIFS storage.
If credentials are not configured, NetBackup marks all CIFS AdvancedDisk and
BasicDisk storage units that use the UNC naming convention as DOWN.