Have 2 server 2012 DC `s and replicating AD
Have this event in Active directory domain services event log on the PDC
Warning DFSR Event ID 5014
the DFS Replication service Stopping communication with Partner XXXX for replication group Domain system Volume due to an error . .......
Error 9033 (the request was cancelled by a shutdown
After that an event 5004
Which in return shows replication working for the other DC