I am having a problem where at very slow speeds the brakes become very grabby. If I am coming to a stop and in the last 10-15 feet need to modulate the brake pressure, the brakes either grab or release. I even noticed the problem at 16 mph today. If I don't need to modulate the stop and can apply even pressure all the way to a complete stop all is fine. This is very disconcerting for me and very uncomfortable for my passengers. Any thoughts. Thanks for the help.