Minecart rail-switch arrows aren't fully interpolated
When riding a minecart, lock-on arrows appear if you can press left/right to switch to another rail track. These arrows are interpolated based on your current position and speed, not on your previous position.
While accelerating, your speed having increased disconnects the arrow from its previous position; for each tic while accelerating, the new T-1 position is different from the old T position. ("T" being the current tic. Frames are interpolated from T-1 to T.)
(The Pop Gun, Homing Attack, and Attraction Shield lock-on arrows interpolate correctly.)