Cruise Control problems of the 2012 Kia Motor Sorento

On 08/12/12 while driving in cruise control at approximately 72-74 mph, I eased out into the passing lane to put myself behind someone going faster. The car suddenly downshifted and accelerated with maximum throttle. I touched the brake pedal moderately to disconnect the cruise control. The car continued at maximum acceleration and in the passing gear. I then applied the brakes with great vigor and the cruise control disconnected and the vehicle slowed down. After a short while I reactivated the cruise control and drove about 60 miles without any further malfunction. I presented the car to the kia dealer service advisor. The car was checked and I was told they could find nothing wrong with the cruise control. I asked them if they reported these very dangerous observations to kia or NHTSA. They said no they never do. Incidental to this event, I had an engine malfunction light on 7/25/12. I took it in for service the next day and told it was a transmission heat sensor. A part was ordered and I was told to drive the car normally. Within several days, I became aware the cruise control was not activating when driving the first time in a day. But if the engine was stopped and restarted, the cruise control worked normally. I duplicated this 3 distinct times exactly as written. The service department was not able to link the difficulty to anything they had seen or read, they summerized it may have been a brake light sensor that failed but the computer dispelled that notion.