this past weekend on our way back from key west i stopped in a rest area for a brake, set the parking brake and streached. when we went to leave, i pushed in the parking brake knob, it seemed as though the brake released but the light on the dash remained on. monitered all the vitals the reast of the way home (150 miles), all ok! set the brake at home, it worked fine, but the light remains on!!! any ideas?