Brakes Failed problems of the 2015 Jaguar XJ

Tl- the contact owns 2015 Jaguar Xj. The contact stated that while their wife was driving approximately 20 mph when the vehicle suddenly accelerated to approximately 50-60 mph. The contact stated the driver stated they applied the brakes, however, the brakes failed to stop the vehicle, therefore, the driver held the brakes pressed down and the vehicle eventually came to a stop. The contact was unable to inform if there were any warning lights. The contact had not contacted the dealership. The manufacturer was not made aware of the issue. The approximate failure mileage was 34,900. Gl.