I had my rear brake master piston seize. lucky only a mile from house so turned around rode home with brake dragging. Ordered a knockoff master but it fits and bore measures the same. Bled the brakes till absolutely no air, rechecked several times no air. I cannot get rear to lock up, they do slow me down. Master will move full stoke. No discoloration on rotor. Did i get a bum master or did i glaze pads/rotor or am i missing something?