horses when height has changed to much when riding it. when you get off the horse you and the horse take fall damage and if you spam jump it works sometimes.

Works with mules,donkeys and horses and works with all speeds
and they don't take damage until you get off ( I went to build limit jump off riding horse and didn't take damage until i got off have to be riding it tho).

how to reproduce
1. Tame horse/mule/donkey
2. Fall from height that would normally cause fall damage
3. Get off
then the horse should take damage.

Also

when going up stairs like in the Screenshot horses tend to glitch out also works with horses mules and donkeys and all speeds

(doesn't happen when going sideways or backward).