Engine shuts off when stopped when in sport mode

What is your question?

I have a 2017 Cooper s 2 door. The car has 2200 miles on it. At 1700 miles i had to have car. Tower to dealership. They claim it was a software issue that has to be updated. I usually use the sport mode. Now with 2200 miles on it the engine shuts off when stopping at a redlight. The car is in sport mode. It does the same thing in mid mode. No do engine lights on dash. The dealers says they can't get it to do what I told them it was doing. They also said no codes came up.