How can I eliminate the wiper chatter that happens everytime I use it? I've replaced the blades and I have tried different brands and sometimes it will be fine but unexpectedly the next time it will chatter. I believe that the problem is the glass as I can see some water spots below the bottom of the blades ( the part that the blade does not contact )that I cannot clean out. I have used an abrasive glass cleaner called "Glass Scrub" but the problem still exists. Any suggestions on a glass cleaner or compound to clean the glass?