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.
Any bugs related to changing nbt during the lifetime of an entity won’t be fixed.