Weird intermittent issue that dealer can't replicate
 

My 2014 manual transmission MINI runs like a dream - and then, after an hour or more on the road, loses power for a moment, particularly when accelerating. It's happened on a hill at 45 miles an hour, on a country road at 30, and 65 mph on a highway. On the way to the dealer, it did it twice. One of those times, it was on cruise control, so I also noticed it pulled to the left when it deccelerated. They haven't been able to make it happen.

Anyone have a clue? Dealer is giving up.