When cats are around vertical end rods, they often get stuck on them.

To reproduce:
1. Place vertical end rods on top of each other.

2. Spawn cats on block that end rods are on or around

3. Cats will eventually get stuck.

My suspicion is that the Cat AI doesn't recognize the end rod as an obstacle and believes it can move forward therefore making the cat stuck. The AI still works, they will look at you and change direction to face you, if you punch them, they will move around.