The rear brakes on my 09 outlander will stay applied sometimes. Rear calliper, piston and pads are free moving. It happens if I use hand brake or the foot brake. Feels like fluid is being trapped in the rear calliper. Could there be something sticking in the foot brake master cylinder/ valve that is mounted to the frame. if I let it sit for a while it will work good for some time, even if I make hard brake applications, then starts acting up again. Any help is appreciated.