I've had my A6, 2.5tdi, Tiptronic, Avant, Sport, Quattro since 2005 (car manuactured in 2000).
I have the same symptoms on mine.
This is "normal" for these tiptronic gearboxes, as the manufacturer states they are adaptive gearboxes.
They "feel" your driving style, and choose the "right" program for you.
Economical, Normal, Sporty.
There are some posts (not sure if here), that willl teach you how to "trick" your gearbox from going back to "gran-ma" driving style. You need to do it daily.
No, it's not about dirty hands.
Just you need to accelerate and decelerate in a combination of some sort, that will keep your box in a normal or sport mode.
I just use is as manual, changing the gears from steering wheel.
You MUST read my other post about the ATF in our tiptronic gearboxes:
https://www.vwaudiforum.co.uk/forum/s...d.php?t=101278
I had 170000 mile when it happened.
So, change the ATF + the oil filter inside your tiptronic box, to avoid what happened to me.
Regards