I remember running into something similar to this many versions ago with child character blueprints. Basically what happens is if I take the skeletal mesh of a character, and both on server and clients, attach it to a specified point, the location is different, usually the server shows it as +94y up and +90y yaw. The same thing happens when I attach the mesh back to its root component in the character BP.
I got around this briefly by making different attach points depending on if it is the server or a client running the logic, however when the pawn returns to its root component on the server side, the offset goes away when the player crouches, meaning if I attach it to an offset scene component, when the player crouches the mesh will end up -94 through the floor.
I have no idea what is causing it, but it’s a pretty severe de-sync between server and client
Added a pic