Mobs do not always avoid harmful blocks

Mobs will sometimes step into dangerous blocks and take damage. This results in them dying over time. reproduce the bug in a flat world with low simulation distance so the game can run at high tick rates.

Steps to reproduce:

1. Build a 5x5 containment chamber with a berry bush in the middle, as shown in the video.

2. spawn a villager

3. speed up the game using the following command /tick sprint 1d

Expected result:

The villager will not take damage from the berry bush.

Observed result:

The villager takes damage and slowly dies

Notes: This works with many other mobs too, such as sheep, armadillos, pillagers and more. Works with berries, wither roses, cacti, campfires, fires.

There are many other ways of reproducing this bug, this is a simpler example. The main cause seems to be that mobs will cut corners to get to their destination more easily, which causes them to partly step into dangerous blocks.