I was flying around a zoo I made on my creative map. It was nighttime, and a half-moon. There were a bunch of zombies at the front of my zoo trying to get to the villagers, or "visitors" inside. They couldn't get to them though, because there was a brick wall that was too tall for them to jump (a whole brick block and a brick slab on top). when I flew to the front of my zoo to get rid of them, I saw a butcher villager that was running in a small triangle-like shape on top of the eating area (The square wooden area next to the booth things, it looks like tables). He was running really fast, and it looked like he was having some sort of spaz or seizure. Just a few seconds after I saw him doing it, he just randomly stop and ran in front of the bathrooms (The metal box at the bottom of the picture). Unfortunately, I couldn't get a picture while he was doing it. I believe the cause was he was trying to run from ALL the zombies at the same time, making his AI get all confused as it was trying to get away from each one. I also have zombie pigmen in my zoo, who might have been adding to it, but I don't think so. I built their cage away from the front so they wouldn't scare the villagers. I circled the zombies in red, the spot where he did it in blue, the zombie pigmen in purple, and the villager himself in green.

Below is how I think you cause the bug.

1. Trap some villagers in an area that mobs cannot get into.

2. Spawn a bunch of zombies (Makes sure the zombies and villagers are aware of each other) outside the fence, so they can't get to the villagers.

3. If your lucky, one of the villagers might start running around crazily like mine did.