@GuacFrog
No problem, glad it’s working out a bit.
Physics can be enabled on both systems, Smooth Sync will just set the Velocity to 0 on ‘non-position setting systems’ and when trying to push things around physically, it’s not going to work right if one system is trying to push an object who’s position is determined by another system. Even if that functionality were to be turned off though, it wouldn’t help because it still tries to set the position every frame.
Basically my understanding of the whole situation is, the reason it doesn’t work is that in order to push the cube (position determined by server), your player (position determined by a client) would have to try to move into a position the cube is, but the player can’t because the cube is being set to the server position every frame. So the version of your client player on the server (position determined client) needs to physically bump into the cube but it can’t.