Okay, I just bought this keyboard from Amazon, and it arrived yesterday. I started using it but there was a problem: when I was coding, I noticed that the 'x' key wasn't working. At first I thought it might be something like Windows lock, but after thinking for a couple of minutes I realized it was a physical problem. I pulled off the keycap and tried cleaning the switches with a soft brush, but nothing changed. The switches were broken. So I think I should take it to a technician, and maybe they can fix it by soldering the keyboard ?