Was riding my horse around, and died by falling to my death when going up a single block. The horse ALSO died. I had no issues navigating with the horse prior to downloading the 1.14 pre-release 1, I used it during snapshots 19w13a through 14b (so 19w13a, 19w13b, 19w14a, 19w14b). It wasn't until I downloaded the update to the 1.14 pre-release 1.

In general, riding around on the horse with the 1.14 pre release 1: stutters when increasing Y by 1, even if it is a single increase to a flat area. Going up steep inclines caused a lot of stuttering of the horse (including the horse taking damage). Going down in Y level didn't cause stuttering issues, nor did it cause damage to either myself or the horse.

What I expected to happen was...:
Climb up a single block

What actually happened was...:
the horse and i both died

Steps to Reproduce:
1. Ride a horse
2. Go up a block/ascend a hill
3. Profit