Passenger side caliper not totally releasing

I had a similar issue with a bad master cylinder. It would lock up over time and then release slowly. The return hole in the reservoir had crud in it and this caused the pressure to build up in the system as I pumped the brakes. If I let the car sit for an hour or so the system would stabilize.

The rims got so hot that I could not touch them and after a while the tire blew.

I also had trouble with a synthetic "non-metalic" piston, that was acting more like what you are seeing.