Horses are not working

Put the summary of the bug you're having here

What I expected to happen was...:
The horses to normally climb up slopes with ease, and be able to dismount them normally

What actually happened was...:
The horses seem to buffer for 1 second before actually climbing the slop. The horse had also instantaneously died when I dismounted it

Steps to Reproduce:
1. Befreind a horse
2. Put a saddle and gold horse armour on
3. Attempt to climb up a slope, preferably a corner slope, and test the buffering

4. Dismount the house (it was in a savanna when it occurred) and the horse will instantly die, despite having full health