REAR CALIPER STUCK?? HELP

[86er]

well not sure if thats right word i bought some rear calipers from yahoo they were suppose to have been just removed from a vehicle in working order, and they certainly do look it calipers wee very clean when i got them and still had in brake pluid no corosion on piston th also came with pads and pads look almost new. now one caliper was assembled on rotor no prob, but the other one seems to be clamped in and is holding rotor also very hard to slide over rotor so its like stuck in a brakein position, i tried pushin it out and it goes out just fine(with force) and spouts fluid and then it comes right back in when i release, anybody have any ideas, hopin i dont need a rebuild cuz im not sure if i can source parts locally so that means more down time but if so so be it, but any solutions? thanks