Transmission Not Engage problems of the 2012 Ford F-350

Tl- the contact owns a 2012 Ford F-350. The contact stated that the vehicle would not engage when shifted into reverse. When the vehicle was shifted into reverse, the contact would have to depress the accelerator pedal and allow the engine rpms to increase before the vehicle would abruptly engage in reverse. The contact took the vehicle to the dealer however, the dealer was unable to diagnose the failure. The contact was advised by the dealer that the failure was common for the particular make and model vehicle. The failure recurred most often when the engine and transmission were warm. The contact also stated that the transmission would shift abruptly when shifting from fourth to fifth gear. The vehicle was not repaired. The failure mileage was 3,000 and the current mileage was 5,500. Kmj.