The rest of the map is fine apart from this room, as soon as you enter your car just sinks thru the floor and destroys it, any ideas how to fix?
If selecting problematic faces, hitting w, then flip normals is not helping (I would guess, especially in colmesh), then I have no idea.
That looks like the normals are flipped. Go into the edit mode (TAB) and search in the right menu (N) for "Mesh Display" and press on the faces button. Now you see the direction of the faces. If you find some wronge faces, select them and hit W to open the "specials" - menu and there select "Flip Normals". After that you can test it again
I think you have two faces overlapping (and one of them looks inverted as well) Select that face again and move it, if it reveals another face behind it, you need to fix it.
