The contact owns a 2020 Ford Explorer. The contact stated that while the vehicle was parked, unattended on an incline, the vehicle rolled backward without warning. The contact was able to place her hand on the brake and stop the vehicle. There were no warning indicator lights illuminated. The contact scraped her knee but no medical attention was provided. The contact stated while sitting in the driver's seat, the vehicle rolled backward. The driver was able to depress the brake pedal. The vehicle was taken to the local dealer where they could not duplicate the failure. The vehicle was not diagnosed or repaired. The manufacturer was notified but no additional assistance was provided. The failure mileage was 22,000.