I'm reading this thread and I suspect my car may have it.

This past end of December I remember driving in 3-6 inches of snow falling up in Illinois north of Danville and feeling the car quickly lose traction a bit accelerating. I thought putting the drive select into Dynamic mode would provide better traction but nope, it felt slightly more slippery so I put the DS back in Auto and drove cautiously slow. Even turning at slightly snowed intersections you could feel the back slipping. Mind you I thought this was usual snow condition experience of driving an A3 Quattro.

I remember the first winter I drove this car back in December of 2014 and I remember driving over snow slush and the car giving me that slipping away feel, that I realized I needed to get winter tires, and got Nokian Hakkapeliitta R2s for which I drive on every winter since. So to experience slip even with good snow tires and reading this thread got me wondering if the Haldex on my car have been bad this entire time.

I'm at about 45K miles so I'm still under warranty. Perhaps I should do some videos of my car doing launch control to see if there's front wheel spin like others did?