Mobs in boats move heads when attacked

The bug

Mobs in boats move / shake their head when attacked.

Note: The mobs sometimes rotate their heads to the very left or right as well without rotating the boat before, see MC-90148.

How to reproduce

1. Put for example a sheep in a boat

   /summon boat ~ ~ ~ {Passengers:[{id:sheep}]}
   

2. Hit it without killing it