It definitely was, the sliders were rusted pretty badly. However the cylinders still worked after I removed the pads and threw in some plywood so they wouldn't pop out. Enough to crush the plywood after a couple pumps. Instead of taking it all apart I cleaned up the pins lubed everything and put it back together. Still have the same problem though so I'll probably get a set of the NAPA calipers. There's also quite a big difference in pad material left vs right, even if the caliper was working fine (now) would the difference in the pad thickness still cause this? I drove it around quite a bit and tried to bed in the left side but it didn't seem to improve... If I get new calipers I'll have to get pads anyway.