Have a 2010 A3 (s line) where all bulbs in tail light assembly work fine. The surround/perimeter lights are not working. So, the tail light does not light up and remains dark. The drivers side tail light works fine. Have played with assembly, sanding metal contact points and making work temporarily. What parts do I need to replace? Just the bulb holder portion of assembly? Bulbs that light up perimeter of tail light? Not sure how to access those, if even possible . Need some help here.