I’ve not encountered this before so I’d thought I would share. A customer had a Lync 2013 pool pair and we were seeing Event ID 4054 errors on one of the Frontends
Sure enough when I ran the get-csbackupservicestatus command it showed the OverallExportStatus was ErrorState. The file in question was located in the pool’s file share within WebServicesCollabJournal and was locked by the server currently associated the backup task.
I stopped the service to allow the service to be moved to another frontend to hopefully release the file.
The frontend server now running the backup task produced an Event ID 4050, which showed the same file mentioned in the Event 4054 log.
About a minute later Event ID 4051 was logged, reporting that the corrupted journal files were fixed.
I then invoked a backup sync and it competed successfully.
Hope it helps.