Mobs shake in minecarts when trying to look around

Steps to reproduce

1. Summon a minecart.
2. Summon a mob so it falls in the mincart.
3. Walk around the mob, or just wait a few seconds.

Expected results

The mob turns smoothly to look at you or look around.

Observed results

When the mob tries to look at you or look around, it starts shaking.