If a player saves and exits the world while on the back of a donkey, when the world is loaded back up the game will enter a lagging and bugged state.

The player will be on foot and can walk around, break blocks, etc., but the donkey's sound effects are still played and appear in the subtitle bar. Blocks are broken, but items can't be picked up and mobs are unaffected by hits until after this period has ended.

After about a minute of this, the player will be suddenly on the donkey again, and the items dropped will be able to be picked up and mobs can be hurt.

In the game's log, the game will output "Received passengers for unknown entity"

It seems as though the player's donkey is still there, just unloaded.

The game functions normally afterwards.

Am important part here is that this lag does not happen if the player dismounts before saving and quitting.

A video ** of this happening: https://youtu.be/81DlbHvnFr8