only occasionally do my left shift and ctrl keys work. I know that I could just use my right set but that's highly inconvenient for my habit of typing the way I do. I've done just about everything dell support has suggested. When I reboot, and then use my shift key, it makes a weird sound, not one I've heard before and not a good one. Any help please - struggling law school student who needs to use keyboard shortcuts with ctrl and a habitual user of the left shift key.