Client sees twitches when server controlled physics actor moves

The title says it all really. I have a pawn with physics enabled. When this pawn is possessed and moved by applied forces, the server behaves perfectly and all is smooth. A client watching the pawn sees it twitch just a little bit about once a second or so. It seems to be a small position correction but why would that be when the client is seeing a replicated actor? Could this be that the replication did not get received for a frame or two?
There seem to be no settings to make replication of an actor reliable (unlike variables where there is). If anyone knows what this is caused by I would be very grateful. Other than that I would appreciate and advice you might have about how would I go about investigating this?