Had similar on a new S4 I bought ended up being a recurring issue so rejected the car for a full refund and getting another R,
Post about it but here's my experience:
Picked the car up new and 3 days later the SOS function went wrong, random alarm going off and message on the display, could happen one every 5 minutes or every 10 seconds, after a trip for to the dealer it was booked in for replacement of the SOS module, only problem is it's behind the dash so it all had to come out. All went well for 3 weeks then the same again, back in to be diagnosed this time was booked back in to have the wiring to the module replaced so dash back out again.
I was getting fed so raised a complaint with Audi, after a bit of a wait they offered a full refund of my deposit.
In the end I had the S4 for 4 months but had really fallen out of love with it so while I had the option decided to come back to the less tech laden R, got a good deal on an a 3 month old, 2000 mile R estate and a few thousand back in my account.
I should add that Audi customer services/VW finance and the dealers I dealt with were very helpful and apart from a slightly longer than anticipated time to look into the issues it was all fairly straight forward.