I always disconnect hbrake cbl.i always fully retract caliper opperating lever.i always squirt a little brake fluid behind piston rubber boot to aid turning and i always slacken the nipple.even so ,every 4th or 5th caliper is beyond saving because some tool has in the past tightened the hand brake cbl to get some grip rather than fixing the self adjstments.totaly f#####g the caliper internals.sorry for language/rant but this make me boil.hope its not the case,but you may need new caliper/s.
caine
August 2008