Sometimes when I press the pedal the golf cart will not respond. It does nothing. I press it several times and it will eventually start going. The works fine while I am going. The sometimes when I try to stop and take my foot off of the pedal it does not stop. It may slow down a little but does not stop. When this happens, turning the key off does not stop it either. I have to put the cart in neutral to get the power to stop going to the motor. What could the problem be?