The problem happens if you open the portcullis and leave the iron door shut then you are able to walk straight through the door.
Not sure if this is really a problem though, because you wouldn't want to put these two doors in the same spot anyway because the frames overlap for some nasty flickering/z-fighting issues. (Although if you cloned a door and changed the doorFrameModel I guess that would be a different story). If you want to have them, just make the iron door open first and it can work that way
