If you have a caliper hanging due to a stuck/sticky pistion, I doubt a flush will bring it back to life.

I have not replaced my rear pads yet so I am not familar with them. Is it possible you have some hardware hanging up the caliber? You or someone needs to take the caliper apart from the knuckle to be sure everything is sliding / floating properly. At 24K, I just can't see a bad caliper already, but anything is possible.

James