The bug

Riding an entity that is far away causes client/server desync. I am not sure if this is distinct from MC-201647.

Steps to reproduce

For these steps, I will use a sheep.

1. Create a new world with this seed: 7747585803886593516.
2. Ensure that there are no sheep nearby.
3. /ride @s mount @e[type=sheep,limit=1,sort=nearest]
4. Notice that the command was successful, but your visual position hasn't changed.

Observed behavior

The visual position doesn't change, and you become unable to interact with the world. Sometimes you get stuck as if you were actually riding the entity.

Expected behavior

You would be teleported to the sheep's location correctly.