I downloaded the latest version, and I keep on running into this annoying bug. The worst part is that it's not a rare bug at all, it's a very common occurence!
Sometimes, when a monster is shot (not just by the player, other mosters also trigger this) it will be randomly teleported around the map, usually ending out of bounds. This can critically affect gameplay as other users have pointed out since, on some maps, it is required to kill specific monsters in order to progress, and they may end up out of reach outside the map.