Transmission Slip Out Of Gear problems of the 2013 GMC Acadia

These symptoms started over 2 years ago and is very intermittent. Driving on the highway, the vehicle suddenly loses power, unable to accelerate and the transmission will not shift out of high gear. The decrease in speed is significant enough that on now 3 occasions the vehicle has almost nearly been rear-ended. Additionally, on the instrument panel the following indicators and messages occur: - "check engine light" - "traction control off" - "engine power is reduced" - "service traction control" - "service stabilitrak" additional symptoms: - loss of power steering - loss of power brakes once vehicle is turned off and sits for a few minutes. The vehicle will start and all of the symptoms above will go away with the exception sometimes of the check engine light. This indicator goes off after vehicle has sat overnight. Note this occurs very infrequently. . . Sometimes months in between. August 2018, dealership (chev automation north, denver, CO) diagnosed as transmission problem. Paid $5800 for replacement. October 22, 2018, all of the symptoms described above occurred again while on highway nearly crashing the vehicle. Wife now refuses to drive the car again. This vehicle is totally unsafe. It is unfortunate that a fatal accident must occur before any real attention is made to fixing a problem of this magnitude with gm vehicles.