So I was testing out the new snapshot, so I simply generated a new world and was messing around with the new blocks and such, then I remembered the woodland mansion, and how I haven't seen one in a while. So, I used the /locate command and teleported to the coordinates given. What appeared before my eyes was something I have never seen. It was a woodland mansion, however all of the wood blocks were gone, and all that was there was some of the cobblestone rooms and the walls, as well as any glass and chests. All the rest was just... gone, like it had never existed. I think this could be because of the new nbt data for wood causing it to bug out, but I looked it up and nobody else experienced this problem, yet... try it out yourself, and see if it happens.