[Markr]

I had a very similar issue on an Audi A8L, along with a speed related drone, which the dealer could not initially diagnose, even with expensive test kit from Germany. Eventually, they put a new car on one ramp, mine on the other and went systematically through everything and only thing that had marginally more play was the propshaft. Audi Germany authorised the replacement and problem solved. Took them weeks to diagnose, but they kept me in new A8’s throughout. May not be your issue, but something to explore. Good luck!