Hitbox of slime and magma cube is offset for some seconds

The bug

Mobs with multiple states have their hitboxs shifted when they spawn (except for the first basic state).

How to reproduce

1. Press F3 + B to make hitboxes visible
2. Use the following command

   /summon slime ~ ~ ~ {NoAI:1b,NoGravity:1b,Size:3}
   

   → The hitbox starts at the back of the baby animal, but then jumps into the middle.

Examples

• Magma Cube: Magma Cube Hitbox Problem (1).mp4 and Magma Cube Hitbox Problem (2).mp4
• Pufferfish: Pufferfish Hitbox Problem.mp4
• Slime: Slime Hitbox Problem.mp4

Code analysis

Code analysis by Marcono1234 can be found in this comment.