Brake caliper pistons not retracting

[J-440]

Evening all. Have a brand new manual brake setup from Wilwood. 12 1/2" with 6 piston calipers for the front and 4 piston rear. My problem is the driver side caliper pistons are not retracting when the pedal is released. Now, the outside pistons are but the inside ones are not. Wheel is hard to turn obviously. So I took off the caliper, disassembled it, inspected and cleaned the pistons and O-rings, put it back together with the caliper shimmed correctly, re-bled the entire system, stepped on the brakes and now I'm back to where I started. The other 3 wheels are fine. Any ideas?