Accelerator Stuck problems of the 2015 GMC Yukon

When the gas pedal is depressed fully, the gas pedal sticks the car continues accelerating. The problem began with initial complete depression of gas pedal to cause some acceleration and depressing brake allowed vehicle to return to normal driving. The problem has worsened over time to the point where both feet depressing on the brake pedal did not affect acceleration and caused smoke to emit from both front brake pads, and the passenger front brake pad flamed up from the heat. The car was driven into a parking lot with the brake depressed the entire time, and turned off. So far, this has only happened when the gas pedal is fully depressed. The dealer told me the mat caused this even though the mat is cut around the gas pedal with plenty of room to not obstruct pedal. The mat also does not slide or move about the area. The GMC dealer told me they took the mat out and did not notice any auto acceleration, and they told me they were unable to depress the gas pedal full to attempt to recreate the problem, to not compromise the safety of the other cars nearby.