After looking at a You Tube video I was able to diagnose the problem which was a bad piston and nut assembly. I contacted Appliance Parts Pros found the right parts and they arrived at the house within 4 days. The repair was very simple. I just unscrewed the filter screen at the lower back of the DW and then unscrewed the piston nut assembly. I install the new part in the reverse order and was complete within 30min. Problem solved.