[stevieturbo]

Do a full scan with VCDS/VAG-Com and see what comes up

Lots of modern shit with CAN controlled lights and circuits can be a total fucking nightmare. And often any fault...can be so obscure and far removed from what you think...that it will never be found by conventional means.

Although checking all bulbs fitted are correct and in good order and all connections/wiring are sound are fairly universal.

 

[stevieturbo]

I work on shit like this for a living. Without any wiring diagrams handy it sounds to me like the lamp driver module is going out. Which is probably the entire body control module on that car. Sounds to me like you have done your diligence on the lamps circuits in the rear. You will at least need to take it to someone that can scan and confirm the module is going out by properly checking the wires from the module to the rear lights. If your car does need a module it will most likely need to be programmed by the dealer in most cases.

Anyone with VAG-Com/VCDS would be able to program the module.

It isnt cheap to buy...but at the same time if you do work at your own vehicles and own VW's or Audi's it would be well worth buying as it isnt horrifically expensive.

https://store.ross-tech.com/shop/cat/vcds/

http://wiki.ross-tech.com/wiki/index.php/Diagnostic_Procedures#Audi