Update by Mega_Spud:
Certain mobs cannot path-find correctly when on ladders, and get stuck there. Those noticed so far are cats and chickens.
Steps to Reproduce:
- Build a small room with a ladder
- Spawn a cat in the room
- Allow the cat to navigate up the ladder
The cat gets stuck on the second ladder block, until it is pushed off.
The cat should not get stuck on ladders.
Cats stays stuck on ladder on the second block.
Chickens too but less often