Hello,
It's possible the your splines in your agitator are stripped out. Maybe you are getting a slight movement in your agitator? If you press down on the agitator while its supposed to be washing does it feel like it wants to turn? If so, I would remove the agitator (yours has a set screw about 2/3's of the way down) and check the splines to see if they are worn.
JP, July 2006