Hi and thanks cignul9,
I have the same trouble even if I use the shifter to the next gear, not just the paddles. Don't understand that...
I bring it up, as I had a 2019 SS A10 loaner from the dealer, and I had tried the same in it... it shifted exactly, sharp and crisp, when I hit the shifter in manual mode each time. Then again, I know that is a A10... vs the A8. Just doesn't seem right that the manual mode would have so much lag to it! As you note, for now, I just leave it in D... it is an automatic.

I know all the M6 guys would be telling me if a wanted a stick, I should have bought a stick.