Door Latch problems of the 2007 Chevrolet Avalanche

The contact owns a 2007 Chevrolet Avalanche. He attempted to enter the vehicle from the front drivers side door and the door handle fell off. The vehicle was taken to an authorized dealer where it was repaired. The failure has since recurred on all 4 doors, including the front passenger side door twice. After each failure occurred the vehicle was taken to an authorized dealer where it was repaired. The failure mileage was 20,000 and the current mileage was 60,000.