Mobs in Butcherblock on a wall
 

Found these mobs all stopped and standing up on a mountainside in Butcherblock Mountains near 445,1800, 175

http://i.imgur.com/i06vyOq.png

Just ran into this on Green, same location. I assume the mobs are wandering and just get stuck here, there's an invisible wall that prevents you from going any further up the mountain.

These and other pathing issues in Butcherblock have been resolved. Fixed, pending update.