Proform XP 580 won't maintain speed

When attempting to start the treadmill at a particular speed the display will initially display the speed you select but the actual belt will start at a much higher speed. Eventually the display will adjust to show a much higher speed. The speed displayed as well as the belt speed will then start slowing down towards the speed you selected but will eventually fluctuate around a speed that is still higher than the selected speed. I tried to calibrate the speed by going into calibration mode and setting the distance window to 85% speed signal but it would immediately ramp the speed up to 15+ MPH (the max speed is supposed to be 10MPH) and adjusting the max speed pot on the controller board had no effect when turning it either direction. I also tried to adjust the pointing of the speed pick up because it appeared to be at an off angle, but that did not help either. I suspect that the controller board is bad, but I'm not sure how to further diagnosis the cause of the problem. Any help on further trouble shoot tips would be appreciated. Thanks!