I've got a sticking rear caliper (passenger side). It eats inner pads for breakfast. I've noticed that the piston is very hard to compress but the slide pins are moving properly. Each time I replace the pad, I exercise the piston 3-4 times for the full travel. It helps for a while but ends up sticking again within a few weeks.

I'm just trying to nurse it along till I can replace all four calipers, rotors, & upgrade to SS lines this spring.