I'm here just to show a pic that I've taken from the board that gave me some head each. I first thought It was a software problem. Then I did some analyzes and I found out that the problem is in the MPR121 soldering. There is a short circuit there because of 3 joints soldered together. The problem is that the store where I bought it sent me another one right the way, but guess what?! IT HAS THE SAME PROBLEM! What is wrong with the board production? This time I gave up on asking for a new one. I decided to try to re-solder it by myself. So here is the picture. Mystery solved.