I, too, have a question about the set screw. I replaced a MacBook Air 2011 keyboard because of water damage and that process involves also taking out the trackpad and putting it back in. After reassembly, I now get phantom clicks (the "click" sound happens as expected, but the Air frequently thinks I'm clicking when I'm not). Could this be a result of over/under tightening the set screw, or is it more likely the trackpad also needs replacement?