I have confirmed that this bug is easily reproduced in a fresh project.
Create BP FPS Template (no starter content)
Select any sk mesh for the default inherit character sk mesh.
Set up 2 keyboard keys, one to host session and one (5s delay) to join session
Simulate with 2 players, host with one, and join with the other.
Observe as the mesh location only remains correct if the host was stationary when the new player joined. If the host (or anyone else for that matter) is moving around when a player join, the mesh location is desynced and offset.
Here is a simple test project to demonstrate the issue
Download
Sample project instructions:
Simulate 2 players (PIE) in editor
Press “G” on one player to host a session
Press “H” on the other player, in 5-10s the other player will connect to the session. Meanwhile, run and jump around with the host player and observe.