Automatic Transmission Control Module problems of the 2015 GMC Acadia

After picking up our new truck we noticed that the vehicle's engine was short jumping at low speeds, especially when in traffic - at first when this occurs you have to almost ask yourself did I hit the gas pedal instead of the brakes. After only a couple weeks of ownership we dropped off our new vehicle to be repaired. Dealer 's GMC certified technician had to consult with GMC corporate to help troubleshoot and then decided to replace the lower and upper engine valve covers, and the transmission control module; which was a quick fix that lasted a little over a week. Now our brand new vehicle is once again a lemon and repeating the original issue. After contacting GMC and after requesting another safer new vehicle since its common sense that a brand new truck should not have any internal engine or transmission problems being that we have a four year old, two year old, and a newborn, I am a concerned for my family's safety; GMC corporate response was "don't you think that 1 car in 300,000 would have an issue". . . At the end we are not talking about a loose belt or wheel out of balance, but an internal problem which there tech told my wife that he could not guarantee that the care was safe during his test drive. The dealer's manager response was "the car is not our problem when it leaves our lot", it then falls under the manufacture warranty; which makes sense, but once again we are talking about a brand new car, not a car that has some usage. Now twenty days in the shop and only 2,000 mile on the vehicle they decided to replace the transmission, but still can't tell us what is wrong with the vehicle; which now when braking on the highway it downshifts hard and almost feels like somebody rear ended you.