after a few tests, i discovered that it might be a fret problem. I did this: played the 3rd string normal, than put the 3rd string closest to the 4th (like bend) and played without any problem. Than i made the same but closest to the 2nd (bad sound fret) and played and the sound is diferrent, worst than the normal and the closest to the 4th string.


after this, i think it should be the fret that is not in the proper conditions, am i right?