I was playing on a multiplayer server, and I was riding my horse around a friend's base. I tried jumping over the fence around their Netherwart patch, and as soon as my horse hit the soul sand both it and I died from fall damage from full health, for both of us. The death message read "{my screen name} fell from a high place". The fence around the soul sand was two blocks high, the Netherwart on the soul sand was fully mature, my horse was spawned in with the command given below, and there was significant lagging on the server; I believe it was ~400 ticks behind (the server host is ServerPro).

Command used to summon the horse:

/summon minecraft:horse ~ ~ ~ {Variant:1030, Tame:1, Health:26, Attributes:[

,{Name:horse.jumpStrength,Base:0.966967527085333},{Name:generic.maxHealth,Base:26}]}