@GuacFrog
Is it better or worse when Smooth Sync is on the player? One other thing is to raise your TimeCorrectionSpeed, but it’ll start getting jittery at a certain point. You could try lowering the InterpolationBackTime and raising the Position Easing Speeds more too. It’s never going to be that great when doing physics if one system is determining the position and then physicsing into an object with a position determined by another system.
It looks like you are going inside of the box a lot. Maybe mess around with Unreal collision stuff so it does that less. You can also try sending an RPC over and moving the box on the server when you hit it on your client.