Cruise Control problems of the 2016 Lexus ES350

I was driving the car on the freeway with the cruise control on when it started to rapidly decelerate and pull back to a standstill. I pushed the accelerator but nothing would stop the deceleration. I had to pull over to the side of the freeway since the car eventually stopped and pushed the button to turn off the cruise control. After a few minutes, I fellt that I could reenter traffic and was able to do so but without the cruise countrol engaged. I took it into the dealer who indicated that they could find nothing. This was a very dangerous situation and I could have been rear ended or gone off the road. If this had happened at night there could have been very bad consequences.