The top arm on my Kenmore Quiet Guard Standard isn't turning. I have gone through all that I could (cleaned debris from screen, made sure it had enough water, checked top arm for clogs and cracks) and still does not move. It is hard to open the door fast enough, but it just doesn't seem to have a lot of water coming out of the top. ?? In cleaning the screen on the bottom, I removed everything (including the plastic cover over the little impeller) that could be removed, and cleaned. Don't know where to go from here.