Owners/service Manual problems of the 2015 GMC Sierra 1500

When I press on the brakes, it feels as though the master cylinder is gone and it is the manual type drum brakes that has air in the line. It takes everything I have to press them and pray it stops!! the vehicle is always in motion when detecting this problem and seems to occur more repeatedly if the brakes are pump quickly in succession before applying brakes or when the brakes are pressed for an extended amount of time then you release and repress it want stop. Another issue is my lane id warning. When turned on at the button, it just beeps at me and shows service light. When I first took it in with the problem, the dealership called me and said all fixed, but it did it before I left the parking lot. They had my truck all day for the issue, put me out of a vehicle and then said they would need for extended time to repair but didn't know there was problem. How do you make that determination when you told me its repaired. I just turned it off and haven't used in 2 years.

March 2017, at 10,881 miles I accelerated to pass a car, lost power, like it suddenly went into neutral. I tried several gears, multiple times, before being able to finally get the manual gear to get me home. Local dealership cleaned up the transmission of broken metal parts. 2,500 miles later, I tried to accelerate after turning into a long driveway, again no power. I tried several gears as before and the manual gear got me to the house. The engine was working and rpms revved, and just like before, felt like it was in neutral. Dealership went above and beyond to try to duplicate the problem. They even checked my truck for the gm recall #14192, NHTSA campaign id # 14v374000, because it was having the same issues. I think that the broken parts found the first time was an incidental finding due to the fact that the problem has happened twice. During all this there has been small electrical issues weak sounding buzzers when I open the door, internal lights either staying on or not coming on at all, and intermittent issues with remote start. My husband bought this truck brand new in March 2016, 6 weeks before he died, so this truck has a lot of sentiment, however, I am very concerned that this truck is unsafe. The fear of being t-boned in an intersection, or suddenly losing power in 70mph traffic is terrifying! I am moving from SC to wyoming in 6 weeks and am scared to death I am going to have problems. I have reported this to the gm complaint dept. Service case # 83120854028. The only paperwork I have are the service records from the local gm dealership.