[BLOCKING Christmas URGENT] TPing non-host player causes entities riding that player to dismount, partially.

Summary: We have an entity riding the player, and when we TP the player, according to all players the entity isn't riding the player, but a new entity will refuse to re-mount, as if the server still partially thinks the player is being ridden.

Impact: This majorly effects our Christmas content, and we cannot find a workaround. We need mounting and dismounting to be totally stable for it to work.

Repro steps:
1. Allow the evoker to ride the player.
2. Open the world to multiplayer, and summon an evoker at the new player. Make sure it is riding the new player.
3. Tp the new player to the host, far away.

Observed behavior:
There is no evoker at the TPed player, testing with /testfor or render bounding boxes.
A new evoker will not mount the TPed player.

Expected behavior:
The evoker is riding the TPed player, and a new evoker will not mount due to there already being a mounted one.