Ok, I hacked it somehow. Seems that running the Movement Component’s Add Input Vector on the owner/multicast will tell Unreal that the actor location has updated.
So I added an Add Input Vector node just after my multicast replication(should work on run on Owner too).
This node simply takes the GetActorForwardVector x 0.000001 to get the smallest vector, so that Unreal still updates the location, but we don’t actually affect gameplay that much.