Exchange Database Error

[willfurby]

Retrospect Multi Server ver 11.5.0.190 running on Microsoft Windows 7 SP1

I am backing up an SBS 2011 server and I am receiving the following error when backing up the Exchange database. However, the individual mailboxes are getting backed up without issue. Any troubleshooting steps would be greatly appreciated. Thanks.

-    11/13/2017 7:30:22 PM: Copying Mailbox Database on ANC (SBS2011)
        11/13/2017 7:30:39 PM: Found: 1 files, 2 folders, 252.8 GB
        11/13/2017 7:30:40 PM: Finished matching
        11/13/2017 7:30:41 PM: Copying: 2 files (252.8 GB) and 0 hard links
        Backup type: Differential
        [*] T-10: MapError: unknown Windows error -3,050
        Trouble reading files, error -1004 (Database Backup/Restore error)
    11/13/2017 7:37:54 PM: Execution incomplete        Remaining: 2 files, zero KB
        Completed: 0 files, zero KB, with 0% compression
        Performance: 0.0 MB/minute
        Duration: 00:07:31 (00:00:17 idle/loading/preparing)