Dear James: ONE (of several) possibility is worn-out rubber underlay pads located beneath the offending keys. Your unit is ten years old and may be showing signs of normal "wear & tear". I avoid recommending any DIY action, and you need to decide whether to spend on repair (ALWAYS BY A YAMAHA -AUTHORIZED TECHNICIAN). The unit will probably have a few years of good use left if you follow my advice. Good luck.
