When riding any adult horse, the horse will clip/snag on any and all block corners, making riding up blocks near impossible without repeatedly hitting the space bar. Going up hills eventually kills the horse, thus killing its rider and issuing the fault of death on 'hitting the ground too hard.'

Steps to reproduce:

1. Find an adult horse and tame it.
2. After saddling it up, ride up blocks.
3. Eventually, the horse will take enough damage to die, causing you to die as well.

(Pictures below are of riding the horse, being killed, and coming back to the area where it died to show its dropped items.)

(EDIT): Included two screenshots of items staying on the ground even though I have already picked them up.

(EDIT2): Putting a block on top of the not picked up item causes you to be able to pick it up, thus causing a duplication.