I've had a strange thing happen to me twice now - One large block of stone disappears from my building. It's as if I had poked it out for a window. No structural damage around the vanished brick. Same place both times. I don't think there has been any stone material left below as it was broken down. The house is structurally sound and I have no idea why that brick has disappeared twice now, with tens of day in between, I suspect a bug of some kind.