Mine started doing *exactly* that in chipped mode. Later on (after ~10k km without doing anything about it) it started doing it in stock mode too.
It's more than likely your DMF. When mine was pulled out (suspecting clutch), the clutch was okay, the DMF was stuffed. There have been plenty of threads and users posting the same thing. Whilst I had my clutch and DMF replaced privately (Audi service said it was clutch, which is wear and tear, so no warranty), the Audi service centre I switched to later told me that in retrospect (and after seeing the DMF), it would have been covered under warranty as DMF issues are warranted but clutch isn't.
If you *really* want to make it slip in stock mode so they do something about it, do a couple of hard launches and I'm sure you'll make the DMF let go with the less torque on offer.