Automatic Transmission Control Module problems of the 2020 GMC Sierra 3500

My truck has been exhibiting hard downshifting at certain speeds, when the powertrain loads up such as a grade change, and requires a downshift. I have complained about this issue to the dealership as early as 2022, and 33,185 miles. The dealership made me pay for a transmission $388. 90 flush which did not resolve the issue. The problem has become progressively worse, to the point where the toll road transponder fell of my windshield during a recent harsh downshifting incident. At the same time there was an existing mil and derating for a def heater and nox sensor failure, so during a warranty visit I asked that this transmission issue be addressed. On Friday March 13, the dealership called and said they confirmed the hard downshifting, albeit not as extreme as I described. The technician said that the valvebody needs to be replaced. At the same time, they performed a tcm flash for the 10l1000 momentary wheel lockup recall. The dealership then said they could not get the truck to set a p0747 code, said that gm refuses to replace the faulty valve body, and recommended I take the vehicle home unrepaired, and to come back when the p0747 code is set. I requested they continue to drive the vehicle. Today March 20 the dealership called and said they could not get the code to set, and that I need to drive the truck and come back when the code appears, despite the truck exhibiting clear symptoms of a progressively wearing feed limit low valve. N242454441 does not seem to indicate a p0747 code is required to replace the valve body. This vehicle is not safe for towing a 20,000+lbs and GMC is refusing to repair a transmission with symptoms congruent with n242454441. The dealership still has possession of the vehicle and wants $360+ in diagnostic labor.