My vehicle was stopped for several minutes on an upgrade, with stopped cars in front of me due to a traffic jam. I needed to keep pressure on the brake, lest my car roll backwards. After about three minutes, brake pedal lost pressure and my foot went to floor. The engine then went into gear and my car rammed car in front. Engine stalled on impact and was hard to restart. Vehicle currently at Jeep dealer awaiting inspection from Stellantis tech team. This situation reported to their customer care center. No warning lights appeared on dash prior to crash. Indeed, this could have been a more serious accident. I will never trust this vehicle again, and intend to take steps to exit my lease.