Sometimes the backup job stops before completion. The backup server logs can give more details on the reason for this failure. Following are few reasons for a backup job failure.
Unable to request a db dump. Already one in progress.
Skipping Large AuditDB for backup
You need to add this flag in the file backupagent.php of production server if the auditdb is too large to take backup.
So the AuditDB will be skipped during backups.