I've found a spot using noclip that isn't seen AT ALL because a door is supposed to have a window. You'll find it at the first half of the map (where the electric water thingy is. The only place where blue water sizzles and kills, the door behind it.)
As Uniq has said it can be opened, though in the second release how to open it is not so obvious (The console on the right in the security control room, but it's timed so you have to be quick returning to the door (There's a button in there so you can get out)). In the next release the override button, will effect ALL (Functional) doors in the sector.