Ive been playing on the beta for more than a month and ive been experimenting with mob cages. In previous versions, a single torch should be enough to stop spawning, or placing slabs on top of the cage prevents mobs from spawning on top. However, in the beta, tjis doesnt seem to be the case. The area around the mob spawner has every block lit up with a torch but the spawner doesnt shut down, making working with the cages very difficult. Please look into this as it seems to be going on for several beta patches