There's 1 power unit for standard bixenons, then there's a cornering unit if they're adaptives, afaik the led unit is fed direct from J519 & an internal headlight module for led drl, but knowing audi, you never know if the main power unit has some interaction, I would go out & test the theory with some shelf headlights we have, but just finding the time.
Ideally you need to remove bumper, swap headlights 1st & see if fault follows, if not then its wiring, if it moves to other side then try swapping power modules & see if it moves still, process of elimination.
If you don't want to or cant do this, then we're up that way around the 20th, you can pop to the show on 21st so we can have a look at it, but ideally needs parts to swap if faulty otherwise its pointless doing any removal of bumper etc to find the fault.