Guys I have issues with the brakes on my GC8 , I noticed last week that on one rear wheel my brake pads were down to metal!,I installed new pads and rotors on the rears .

Turns out the piston was getting stuck ,had the rear calipers overhauled at a local brake place , then I installed them yesterday . yesterday and today I tried to bleed up the brakes but they are just not right ,have to pump the brakes 2 -3 times for a decent stop . Plus I now see ,that same caliper is sticking again!!??, Im baffled as to whats going on ,I might have to try get the car to the local brake place because Ive never had, this issue on any car in my life so unsure what the problem is