Configuration Manager 2012 R2 Endpoint Protection client – failover path scenario

EP definition and Engine update failover scenario:
A customer has set UNC as a failover option in EndPoint Protection on a CM12 R2 environment. If the connection to the Configuration Manager is lost, then he may face the following behavior:
The clients fail over to UNC as expected , they download the full EP package (100mb +) (mpam-d.exe , mpam-fe.exe, nis_full.exe) which as a result is causing high network utilization...

So,why the clients downloaded the full package?

Answer:
This is the current default behaviour of the download from UNC update method...
It only grabs the full definitions, even if deltas are available from the share...
This operation collects the full definitions, even if deltas are available from the share and this is a known issue for the Product Group.
Currently, we don’t have any specific  information if / when there will be a fix for this issue, but it will probably be addressed in some EP client update…