I don't really know if this would really be classified as a bug, but when you create a warden spawner, the little warden's head is permanently tilted in the spawner and you would expect it to be straight instead, as other mobs are in their default position with a straight head, you would expect the warden to also show up like that in the spawner. I have attached an image showing the tilt of the warden's head in the spawner