Strange one.

I've saved a few sticky rear calipers by winding them in with a retraction tool then working them out with the handbrake lever on/off about 20 times then winding them in with a retraction tool then working them out with the handbrake lever on/off about 20 times and so on and on and on until the caliper feels like it has freed up.

Don't forget yours are recon'd and may have sat on a shelf for a year or two and despite being 'new' might themselves be sticky. The seals no doubt are new and the bores checked but I bet they did nothing in the recon to the actual adjuster mechanism for the handbrake except paint it!

In and out, in and out and least 5 times is what you need to do