I have a mystery I was hoping someone on here could shed some light on, haven't seen a prior thread on it so apologies if I missed one..

Purchased an '06 A4 Cabriolet with ~70k miles. 1.8L turbo, 6-speed CVT transmission. Shortly after purchase I noticed that once the engine warms up, accelerating regularly from 0 the whole car will start bucking pretty hard at around 20mph, almost as if it is struggling to slip into the next gear (but not of course, bc its a CVT). This only happens once the car is warmed up, and can be induced faster if going up a hill or applying the handbrake a bit. When it is happening, I can click the shifter from automatic into manual mode, and it immediately disappears. Even just clicking it out and back again works. Also doesn't buck in sport mode.

Audi dealer had it for 2 weeks, replaced some minor valve to no effect, then said they found metal shavings in the transmission fluid. I had the trans replaced with a refurbished one, but the same exact issue continued. Dealer I bought it from seemed to think it was a "pressure" problem, but wasn't able to back that up with anything concrete.

Anyone see this before? Ideas? Computer? Torque converter? I'm lost..