Horse Causing Suffocation

[alpha 1.1.0.3 332621]

Summary: While riding a horse, jumps sometimes cause the horse to disappear, and the player suffocates to death. The example is from DestructoBot, but we have witnessed this on Adventurer's Dream as well.

Impact: [Blocking] This breaks the player experience. The player dies for seemingly no reason. Necessary to launch this content. If this is not fixed, we would not in good faith be able to release DestructoBot 5000.

Repro Steps:
1. On Destructobot or Adventurer's Dream, spawn a horse
2. Ride them around and jump

Observed Results:
Player falls to the ground, starts suffocating. The horse (and sometimes more entities in the area) disappear.

Expected Results:
Player remains mounted, doesn't suffocate, no entities disappear.

Screenshots/Videos attached:

Notes:
This may be behavior pack related, but it was not happening in 320754 or 327642. It seems to be inconsistent whether the dismount suffocates you or not, but the horse disappears either way.