When going to the boomers land the guy said there was a railroad. I used this as a way there in the tunnel there's a room if I try to walk up the steps I fell though the floor. This doesn't kill you it sends you to the boomer side entrance I tried this again I walked through the floor and walked back after doing this I could walk through all Walls in the tunnel (Outside the map) there is only some parts of the wall you can stand on the outside. It seems the platform is built on rocks (what I used to stand on the outside of the map). This bug is fixed when you exit the tunnel or fall through the floor.