Finally got the funds (and guts) to bring my A6 to the trans shop for a full diagnostic. From my experience, it's the converter, but there are no DTCs, so maybe I caught it quick enough Sometimes (not always) when it goes to shift, it seems the converter completely comes disengages and the car revs like it's in Neutral. On downshift as well. It's not a gear slip, it revs too fast for that. I tested the gears in tip mode, going easy in 1st, then heavy on 2-5. Also, the converter shutters when it tries to lock up in 4th and 5th, and I also hear what sounds like bearing noise from the bellhousing area. I read somewhere these converters were also notorious for the needle bearing in them blowing up...

Fingers crossed; I love this car