Every once in a while I have an exterior door that refuses to be installed correctly. When I add the exterior trim it remains on the interior. I have reinstalled the doors, flipped them and reversed the walls to no avail. Quite often I have to take out the entire wall and redo it to make things work. All the other exterior doors in the project work fine. Obviously, I am doing something wrong but have not been able to find out what. Any suggestions????