, there is supposed to be a hill holding feature on the A6 that will momentarily hold the car while you move your foot from the brake to the accelerator. In your case, the obvious possibilities are:
- the hill isn't steep enough to engage that feature
- you're wanting it to hold too long and it's letting go
- or there is a failure and it should be checked by the dealer.
Will be interested to learn what you determine is the issue.