I've got a mob farm room 30x30. It's all rock (mostly cobblestone) and totally enclosed and unlit. There are 6x6 spawning pads with water canals between them. The room is centered below my house. The surface of the pads is 24 blocks below my house floor. Most of the nearby caves have been lit up. Absolutely nothing spawns here but bats. An identical build on my Xbox One spawns mobs like crazy, and I haven't even lit up nearby caves yet on that world. Is this a bug, or are the spawning rule for PE drastically different? Yes, I have checked to make sure it's not on peaceful.