Hi! I have a Casio Privia X130. It's 3 years old now. I've only been using the classical piano sound to practice. Recently that particular sound became off. When I choose classical piano and press some keys, there will be random noise instead of the correct tone. All other sound works just fine. Any idea how bad the problem is and how to get it fixed? I've checked repair stores and a bit worried about $80/hr rate... Any advice is greatly appreciated!