I am the owner of a 2000 2.5tdi quattro a6. Two days ago i realised one of the rear doors wont unlock or open. I can see the door lock nub trying to pop up bit it won't. When you pull the inner door handle it syill wont open. So I cant even take the inner door card out as the door wont open its driving me nuts. Any advicw/help would be greatly appreciated.