Networker 8.2.4 CCR VS Networker 9.X CCR

Hello and Happy New Year!

So, I have a situation that's driving me a bit mad...

We have 2 DD2500's geographically separated, Networker server and primary DD2500 are in one site and the CCR DD2500 target at the other (multiple tenants exist on the target device).

For some reason the clone replication between these two devices with Networker 8.2.4 is a lot slower than the replication than the clients who use Networker 9.0.1  They all have the same VPN tunnel sizes, using the same switches and routers -the only difference is the version of Networker.

Does anyone have an idea, or suggestion on where to start looking for potential cause?  I'm starting to feel like maybe it's Networker - since the only difference between the other sites and the one having issues is the version of Networker.

Anything helps and much appreciated.

Thanks and have a good day.

Sal