On several occasions the car will violently stop as if we have crashed into something but there is nothing there. There is no warning before this happens even though we have the alert setting turned on. This has happened while we are reversing and moving forward. This puts us (driver and passengers) at risk because it is such a sudden and violent stop that it hurts our bodies (neck/back) and it is very stressful. It has not been reproduced or confirmed by the dealership yet