"Backup Oplog Behind" alerts occur because the * Manager backup service hasn't gotten an oplog from the Backup Agent in at least an hour. This can be caused by:
- Backup Agent down
- Backup Agent overloaded
- Backup Agent not being able to reach the replica set
- Backup Agent continuously restarted
The user should be directed to check the Backup Agent logs in Cloud Manager and on the Backup Agent host to find out which of these occurred.
Perhaps this would go into the Cloud Manager & Ops Manager FAQ?