Instant health arrows cause infinite healing to horse when riding it and being shot by that arrow.

When the arrow of instant healing is shot at a horse you are riding or in a trajectory that it will land on the horse you are riding the arrow will continuously bounce. Each time it bounces it heals the horse meaning you can infinitely heal a horse. This would probably be true for the instant damage arrow too, but it causes enough knock back that it only triggers once and then the horse is pushed out of the way.