When you change the motion of a snowball with a command, instead of instantly changing direction it goes on a bit and glitches back to the right position where it should be after 0.5 - 1 seconds.

Best example, if you spawn a snowball and change it's motion to 0.0, 0.0, 0.0 it first looks life it is flying away, but when you change your position you see it's actually in your head.