Just purchased a new YAS 62II found the middle C, B and A are a little flat about 25 Hz off the mark, compared with the rest of the notes in the lower register and with the octave they are all about 25 Hz sharp, this is with an electronic tuner. I did not have this problem with the 475 which had very accurate intonation. Could this be a fault with the instrument? Or is it that I need longer to get used to it?