Engine Grinding Noise problems of the 2019 Ford Mustang

While driving my gt350 on a highway at around 55 mph the engine made metallic grinding noises suddenly, and without warning. I instinctively pressed in the clutch pedal and then engine stopped spinning and locked up. I was fortunate to be in an area with a pull-off area and thin traffic. It could have been very dangerous at higher speeds, in thicker traffic, or with a less experienced driver. Once stopped, I checked the car and confirmed that the starter could not spin the motor due to mechanical failure. There were only about 450 miles on the vehicle when this happened. I was later told by the dealer that the engine had an issue with a rocker and valve, which caused the engine fail and lock up. A replacement engine also had 'valvetrain noise' and was determined to be no good by the dealer. I did not see or use the car with that engine. Beyond that, this issue is still unresolved as the car has not been repaired.