If you suspect clutch slippage, do not start by looking for clutch position in VCDS. Instead start by comparing driveshaft 1 & 2 to engine rpm. If either of the driveshafts match engine rpm then the applicable clutch is NOT slipping. Conversely if the shaft associated with the gear in use differs from the engine rpm there is a degree of slip occurring. At times you may see simultaneous slip on both clutches during start off as the car launches in 1st but never fully engages the K1 clutch before K2 comes into play engaging 2nd. This is normal. I guess the issue here is how much slip is acceptable, if this is indeed the cause. But this method should clarify things for you.
You will only need to look at a single Group and 3 blocks so you will be able to pull a meaningful sample rate.
005,1,transmission input, speed 3 (G641)
005,3,transmission input, speed 1 (G632)
005,4,transmission input, speed 2 (G612)
These blocks are for the DSG7 however it is likely they will be the same for the DSG6.