DPM syncronization failure on Secondary Server

I now have an environment of Microsoft Data Protection Manager 2012 R2 set up as a replacement for Backup Exec 2010.

Despite the lack of some features, it has been performing quite well. However I recently started receiving email notification of errors and it relates to my secondary DPM server.

The primary DPM server exists in the head office, and provides back up of Hyper-V VMs from my main cluster. The secondary DPM server exists in a branch office 300KM away and provides back up of the primary DPM server.

 

I started receiving errors like the following from the Secondary server to individual resources on the primary:

Synchronization for replica of \Online\servername(servername.clustername) on PrimaryDPM failed because the replica is not in a valid state or is in an inactive state. (ID 30300 Details: VssError:The writer experienced a non-transient error.  If the backup process is retried,
the error is likely to reoccur.
 (0x800423F4))

 

Every time I tried to perform a consistency check on these resources, it would begin and then end within 30 seconds.

To be honest I didn’t have a lot of time to troubleshoot this one. I tried restarting both DPM servers as well as the Hyper-V host and VM itself, and none of that seemed to have an impact.

At some point I noticed that the resources giving the errors on the Secondary server hadn’t had a recovery point on the Primary server in quite some time.

I forced an Express Full Backup of the VMs on the Primary server and allowed it to complete (successfully). I then initiated a consistency check on the Secondary server protected resources, and it too completed successfully!
Where I’m still confused is why didn’t I receive alerts from my Primary DPM server that recovery points were being missed?