^{Update by Mega_Spud:}
Summary:
Certain mobs cannot path-find correctly when on ladders, and get stuck there. Those noticed so far are cats and chickens.

Steps to Reproduce:

1. Build a small room with a ladder
2. Spawn a cat in the room
3. Allow the cat to navigate up the ladder

Observed Results:
The cat gets stuck on the second ladder block, until it is pushed off.

Expected Results:
The cat should not get stuck on ladders.

Screenshots/Videos attached: Yes

Notes:

Original Description:
Cats stays stuck on ladder on the second block.

Chickens too but less often