I see alot of F48 and F39 owners complaining about this here at work. There is a software update but like others have stated it doesn't always correct the lag.
It's not really an issue with the transmission but with the electronic gas pedal. There is a delay between when you push the accelerator to the computer.
A sprint booster would eliminate the so called lag. I installed one in my e46, e82, four MINIs and my F48. Look mthornto88 said it gets rid of the lag. I always drive around with both the sport on and extreme + on the booster.
Here is a write up from my former employers
https://www.bavauto.com/newsletter/2...newsletter.pdf