If it were me I would be squeezing the Pistons back and see if you pull the calliper in and out. This should prove the sliders are free and should be able to check the pads are free too. Make sure you get a bit of heat into your brakes before it goes on the brake rollers too. If your tester is ok he will check before he logs it on to check. If the prob persists I have swaped the pads from left to right in the past and had good results. This is assuming your discs are not to badly grooved/worn. Hope this helps