What condition are the dream-doors in? Are they open or closed? Perhaps locked? A barricaded door may symbolize your need for self protection.
If someone is knocking on the door, are you letting them in or not?
Running through different doors may show you're trying to find solutions to a problem. A door connection outer and inner worlds may represent the connection between your conscious and unconscious.
If a door is missing, keep looking at your situation from different angles until you find a way.