Having issues with dealer about real reason for brake failure...on my w164 2007 My rear brakes got stuck leading to one rear wheel getting red hot. Merc sent out recovery who told me the caliper was stuck and brake pad worn. (All pads were previously around 40% worn) It was recovered and dealer said as they released Pad, Pistons went Back in caliper on their own so no caliper issue. I was told different reasons for it happening - damp pad with grit between pad and holder then told it was corrosion. So recommendation to have new pads discs and brake fluid change on rears... Had no choice but to have done... Drove home and same issue wheel and disc hot and all other 3 wheels cold !!!!! So recovered again and now dealer says despite road testing no issue found ??? I have extended warranty with merc but they say not proven caliper failed? Could this be intermittent sticking with caliper ? Any ideas ? Not happy with service I've received and car now with dealer for over a week !!!