Currently Attempting the exact same thing, also with the same issue. All replication so far has went so smooth, but this time it has been hard as it is an actor in the map using an overlap event, It’s not completely the cast to your character that’s the issue it’s also the fact that the overlap event fires for each client and the fact that each client owns there ‘own version’ of the actor. The whole thing has to change a lot and the overlap event must only trigger an event on the server, then the server will have to do everything on the overlapping pawn.
Anyways not much more to add YET except I am working on it 