The bug:
Spawning mobs*** against a wall will cause them to get stuck or suffocate.
*See 'affected mobs' for list.
Affected mobs:
Spider
Polar Bear
Turtle
Donkey
Ghast
Mule
Skeleton Horse
Zombie Horse
Steps to reproduce:
1) Make a wall (can be any size)
2) Grab a spawn egg of one of the mobs listed in 'affected mobs'.
3) Use the spawn egg on the wall.
Conclusion:
Hitboxes of entitys are too big causing them to glitch into the block.
See the screenshots I attached for more information.
Video: https://streamable.com/vrzah (video file was too big)
Related issues
Attachments
Comments

[media][media]

See MC-103934