I think that I am having the same problem, only that it showed up in a different way. My drivers side caliper was not seized, but I noticed that I really had to wail on the clamp to push the piston back into the caliper. I realized that this was not normal, it should not have been that hard to push back in. I did buy a reman caliper and I picked up a pair of calipers from the junk yard for a few $ over the core charge on the reman. The DS caliper from the junk yard looked like it was maybe a year old at most. So I returned the new caliper and I am in the process of cleaning it up, painting it (red), and putting on new rubber to overhaul. I also am putting on new rubber hoses. My reasoning is this, and this may be related to the "check valve" issue that you described. The pressure had to be high to push the piston out for braking and that expanded the hose more than normal. Then when the master cylinder returned to the resting position, a vacuum collaspe occurs in the hose because of the weakened hose - maintaining the pressure at the pad/rotor. Just a thought, but the high pressures compell me to replace the hoses as well. I was surprised about how easy it is to overhaul a caliper, and will never buy a reman/new caliper again. The other thing that I noticed was that this causes glazing on the rotor. That is where a thin layer of shiny metal covers rusting metal below - causes rotors to rust because of high heat and slow release of the pads. Also eats pads because of the rust on the rotors. Wondered if anyone else noticed this as well?