The other thing, this stuck piston we're talking about - I tried hard last night before giving up for the day to push it back in - the other 3 move out AND in freely, but I couldn't for the life of me force this one in. Just in case that system helps someone with a diagnosis.
I did that first time I did mine, they started binding within a year or so and needed redoing.
You might be alright with just pushing out each pot, greasing it and pushing it back in. I'd consider taking them apart and greasing them properly while the seals are still new, dunno if that's appropriate but it's cheaper than redoing them with new seals next spring.
thou shalt not kick