Audi S5 B9 RPMs drop under acceleration when engine is cold

[Sebnagy22]

I've had this issue for a few months now and can’t get to the bottom of it. When starting the car cold and pulling away the rpms will drop around
100-200rpms when accelerating and then rise back up, it also only happens in second gear and sometimes but very rarely it happens in first gear. The rpm drops only ever happen when the car is cold. It doesn’t happen once the car has warmed up. I had a gearbox leak which has now been fixed but it hasn't solved the issue. Also, sometimes when I let go of the accelerator the rpms will increase slightly and the car feels like it's accelerating on its own, this again is also only noticeable in second gear.
Anyone know what it could be? Here's a video of it happening https://youtube.com/shorts/qlyPGdYh2ds?feature=share

[ForceOfG]

My one and only guess is its torque convertor lock up. Don't know what the procedure is on Audi's but in other cars the TC has different lock up speeds and pedal request limitations at cold and warm operating temps that tell the TC when to lock up. I'm betting if you gave it more beans the RPMS wont do that since the TC will likely stay unlocked longer.