Arrows shot from bow bounce on horse when moving or not and damage if fire arrows

I expected to see that arrows i shot would go through the horse when i shot downwards.

What actually happened was that when was not moving and shot downwards with a regular arrow it bounces around on the top of the horse doing no damage. But when not moving and shot downwards with a fire arrow the fire constantly hurts and flipping around on top of it until it dies and then the arrow drops to the ground. When moving the regular arrow does not affect the horse but the fire arrow just damages the horse and then drops to the ground. This happens in both survival and creative.

Steps to Reproduce:
1. Get a fire bow or regular bow and then some arrows
2. fire it downwards
3. arrow then bounces around if not the horse is not moving and hurts horse if it is a fire arrow.