Hi hopefully these instructions will match your A6
Remove cover on luggage compartment side trim.
Remove nut -arrow-.
Carefully release the cover -2- from the rear light -1- using the removal wedge -3409-.
Pry rear light -1- at outer edge out of clip nuts using removal wedge -3409-.
Remove rear light from body opening.
I hope these help and if I can help further please feel free to ask
Hi there are only the pictures for the one side so it would be a mirror image of what I sent.
I would certainly look at all the connections on the lights before doing anything else.