The contact owns a 2021 Ford Bronco. The contact stated that while her son was driving at an undisclosed speed, the brake pedal was depressed but failed to stop the vehicle immediately. The brake pedal was extremely stiff while depressed. The brake warning light was illuminated. The vehicle struck a speed sign, causing the front driver's side mirror to shatter, and glass shards flew inside the vehicle, cutting the contact's son's left hand and arm. Medical attention was not received. The air bags did not deploy. No police report was filed. The vehicle was taken to the dealer, where it was determined that the brake vacuum hoses, front driver's side mirror, and quarter panel needed to be replaced. Only the brake vacuum hoses were replaced by the dealer. The vehicle was not repaired. The contact stated that prior to the accident, the vehicle was taken to the dealer for the same issue; however, the dealer was unable to duplicate the failure. The manufacturer was made aware of the failure and advised the contact to file a complaint with the NHTSA Hotline. The failure mileage was 20,553.