While driving at highway speed there was a sudden metal on metal sound. shortly after this noise started there was a burning smell and then visible smoke from the wheel. i pulled over to evaluate the noise and smoke. the radiant heat from the wheel caused the fiberglass panel on the side of the car to heat up. this heat caused a 3rd degree burn to the tip of a finger. the vehicle went to the dealership. the dealership evaluated it and stated the drivers side rear caliper froze. the day after the flex was returned "fixed", the passenger side caliper froze. it did the same thing as the drivers side (made the sudden metal on metal sound, smoked and heated up). the flex was towed back to the dealership, where the other caliper was replaced. the flex was returned later that day "fixed". upon driving home, both the right and left rear caliper re-froze. after multiple visits to the dealership, i decided to take my flex to a trusted brake shop for a second opinion. the shop stated both right and left rear calipers were seized. they advised the parts were incorrectly installed. they were able to make the necessary repairs and corrections to fix the right and left rear caliper. i have had no issues since the shop did the repairs.