When I attach 2 cubes together with movement and components replicated, set them to simulate physics, and push them around the child object jitters a lot, especially when the parent rotates. I’m seeing this in 4.26 and 5.
Here’s a demo, but it can be seen when you do this in a fresh third person template too: Physics Networking Issue - YouTube
In the video I’m a client and pushing the parent block, you see the child block rotate and jitter.
Is there a fix for this?
So I think this is happening with replicated rotating physics objects in general, it’s just more noticeable with an object attached and far away from the center.
What I think is happening is the replicated rotation and the clients object rotation are not normalized, meaning the client might see the yaw at -50 but the replicated update is at 310. So I imagine that the client is trying to snap to the “correct” rotation because it’s so far away. I cannot confirm this is what is happening though.
Did you configure collision to ignore the pawn capsule? Also are you using a physics handle?
FYI, linked vid is not available.
I have no idea what I did but the jitter is gone now on both engines. 
You really don’t remember ? Because I think I have the exact same problem… A simple ball with physics on replicated, in particular when the client push the ball.