In execution mode, on overground map i found map bug. It is first building on the left side (right part of the building) from defenders. In that room there is a window looking the corridor where attackers would came, if they went right from their spawn. (on first screenshot you can see a part of a train for easier orientation)
If you would walk to the window and keep on walking forward and right, you would go onto the “invisible stairs” that would lead you to that wooden platform. (also seen on first screenshot)
I don’t think that was intended, or there were missing some stairs 
