When you travel a longer distance away from the place where you spawned lastly to a known location that you have been in Minecraft version 1.13.2 and the chunks load slowly, it can happen in version 18w50a that unexpected structures appear. In my example, a big mountain was generated that cut off half of my self-created village as well as the large part of the copy of an end city. Short time after I regarded what happened to that place, the game crashed. The pictures below show this place in version 1.13.2 in comparison with version 18w50a.