I'm seeing some really odd behavior that I don't know how to explain. Whenever an enderman places a block, the block beneath it turns into an empty mob spawner.
I recently added Yung's "Better Mineshafts" and "Better Caves," as well as updating Enhanced Mob Spawners. The creator of Enhanced Mob Spawners has stated that his mod does not change anything about spawn generation, but I can't find any mention online about this behavior from endermen associated with Yung's mods or anything else.
Has anyone else seen this? Here's a view from inside a cave where one or more endermen were active a while ago. You can see the two mob spawners under dirt blocks. Neither spawner has a creature in it.