I agree that I wouldn't have taken it back from them with the , "Sorry, can't figure it out and fix it" decision. With you taking it back, the time you have it with the brake issue still going likely isn't counting towards the time it is down for repairs under most lemon laws.
GM Engineer was supposed to come to the dealership Thursday for the third time and they canceled and told me I needed a Cam adaptor for the IBC to work with my new Montana Fifth Wheel. I informed them they are installed from the factory and my coach has one. He evidently hadn’t talked to the other engineers or dealership because the truck works on no trailers and they know that. GM Customer service called today a I told them I want a new truck. I have reservations in Florida the end if the month. Not looking good.....