The contact owned a 2021 Ford F-450 Super Duty. The contact stated that while driving 35 MPH on an 8 percent decline and pulling a trailer, the vehicle slightly responded upon depressing the brake pedal. Additionally, the transmission failed to downshift and was stuck in 10th gear. The contact pumped the brakes; however, the failure persisted. The contact drove into the shoulder of the roadway, and the vehicle was able to stop. The contact noticed smoke, and upon inspecting underneath the vehicle, the contact noticed that the rear brakes were on fire. The contact was able to extinguish the fire with a fire extinguisher. There was no injury sustained. The vehicle was towed to the residence of the contact's friend, where the trailer was detached from the vehicle. The vehicle was driven to the dealer, where it was test-driven, and the contact was informed that no failure was found. The vehicle was taken back to the residence of the contact's friend. The contact stated that upon depressing the brake pedal to start the vehicle, the brake pedal travelled all the way to the floorboard. The vehicle was taken back to the dealer and traded for another vehicle. The vehicle was being repaired. The manufacturer was notified of the failure and referred the contact to the dealer for assistance. The failure mileage was approximately 78,000.