2020 GMC Acadia drivetrain & axles problems

When the vehicle is already in motion, it automatically shifts out of drive and I am left in the middle of the road unable to accelerate for a few seconds until the vehicle automatically shifts back to drive. This happens after pulling out of my gravel driveway which is a slight incline, and onto a highway. The cause is unknown.

The contact owns a 2020 GMC Acadia. The contact stated that while driving at various speeds, the vehicle was shuddering. No warning lights were illuminated. The vehicle was taken to a local dealer, where it was diagnosed that the torque converter needed to be replaced. The vehicle was repaired; however, the failure persisted. The contact stated that while starting the vehicle, and while driving at various speeds, a buzzing noise was heard coming from the engine compartment.