The shift has a simple reason: the black area on your map contains a room:I think we should call it the "unknown room" (because we don't know the room's purpose)Btw: the whole Power Plant complex is very "dynamic" and some rooms change during gameplay. You'll have a hard time if you try to create a map by only stitching the room images together.EDIT: someone on reddit asked if there are more unused rooms. Yes, but it looks like these rooms are not integrated into the map such that changing doors would make them accessible: http://imgur.com/a/CYCeY