A couple of years ago I got my wife a used 2014 A4 (60K miles) with manual transmission thinking I would avoid the risk of a really expensive auto trans failure. Haha! Sure enough, it has now developed symptoms reminiscent of a slipping clutch, but with significant differences from my past experiences with slipping clutches.
First of all, it is worst in 3rd gear, and harder to get it to slip in 5th and 6th, which is kind of the opposite of what I'd expect of a slipping clutch. Second, it is not consistent: sometimes it won't slip, sometimes it will, under the same general conditions. Third, the slipping is only momentary: rpms surge and then drop back to match road speed within maybe a second, even if I resist the instinct to back off the throttle because something is clearly wrong. Fourth, there are other symptoms that I can't square with a slipping clutch. A couple of times when I have accelerated hard, the engine has shuddered and lost power dramatically and thrown a code. I wrote it down somewhere but now can't find it, but it was some vague generic code, which went away after some sequence of turning the car off, or downshifting and accelerating hard again, or Venus going retrograde or something.
I now know that the A4s are kind of famous for slipping clutches, but this seems very different from every other slipping clutch I've had (and I'm old enough to have had several!) I confess I don't know enough about the AWD components of the drivetrain to know if there is something other than the clutch that could be slipping, so I'm wondering if anyone here has any thoughts?

 

Could it possibly be loss of boost? I know the 2.0T engine had Wastegate issues sometimes.... do you remember the code you had? Not sure a slipping clutch would set a fault....