2006 Focus brake problem

So far no fix by the dealership. The problem started about 2 months ago. The brake pedal normally has about an inch play before activating. Occasionally, the brake pedal
has no play at all. I have noticed that when this happens, the brakes are binding and tend to slow the car down, to the point that it may drop down a gear just to keep going at a given speed. One time I was doing 70 on the interstate when it happened. It dropped down two levels, and I had the gas pedal almost to the floor and it was still lowing down!
The brakes have never locked up entirely, but at a stop the car will not roll even on an incline. A couple of times I have noticed that the car would even slow down when going down hill! It generally frees up after a period of time, to the point that the service dept has only seen the problem once. They determined that the right front brake was hanging up (temp measured at over 525 degrees, so they replaced the front disc calipers, rotors, hoses, the whole nine yards - both sides. And road tested. But by the time I got home (10.5 miles), the problem had resurfaced. It appears what they fixed was simply a result of whatever the problem is and not the actual problem.
It seems to go away after a short time with the engine off, though I really haven't been able to track the symptoms.
Got to take it back to the dealer, but he seems to be stumped at the moment, so I'm looking for suggestions.
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