The bug

When you had an ArmorStand as passenger on a boat, drove a little bit with it, and then exit the boat, for the client the boat often starts rotating.

How to reproduce

1. Use the following command, on a one block wide tower
   Example command

   /summon Boat ~ ~1 ~ {Passengers:[{id:"ArmorStand"}]}
   

2. Enter the boat and drive a little bit
3. Exit the boat
   The boat might spin on its own now