Okay so I was playing with a few Hungarian friends. They were complaining about me "slipping" and teleporting. I was moving with a joystick when I was slipping, I started using WASD and i wasn't slipping.
So, I've noticed it's all because how LU sends inputs. LU doesn't seem to send joystick inputs, but still sends positions, so it will have you teleporting (or slipping).
Now, I didn't say teleporting WITH slipping. It's a different matter and has to do with how controls work.
There are two control types: STANDARD and CLASSIC. LU switches to Standard when you join, but you can easily change to Classic. (Please don't remove it completely though, some people like moving that way!) So, let's say there is a Classic player and a Standard player. The Classic player presses left to move. Now it would cause him to move left AND down because the camera rotates, but in Standard this doesn't happen, so the player simply moves left then teleports a bit back. Simply put, ALL players move by YOUR control type, and not their control type.
Anyway, here is how the Classic(C)-Standard(S) desync looks like:
S S S
Please fix these issues, they are REALLY bugging me, especially when I try to record!