2023 GMC Sierra 1500 brakes problems

electric parking brake turn on while towing behind Rv did damage to driver side ,had towed it for 340 miles before this happened it is not in my manual to disconnect the ground cable ,when I took it to dealer they gave me a paper stating I need to disconnect the ground cable after putting truck in neutral I told them GM should have put that in the manual instead of tell the dealer .I have turned a claim into GM thru bbb auto line have not heard back yet

The contact owns a 2023 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the brake pedal was depressed; however, the brakes failed to respond as needed. The vehicle was towed to the dealer to be diagnosed. The vehicle was diagnosed with an inoperable battery, which caused the brake module to fail, preventing the brakes from operating as intended. The vehicle was repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 29,000.