Dennycrane2000

Hi When I turn on my Yamaha CP33, sometimes on random occasions it changes the sound to organ and remains stuck on this sound indefinitely. I have opened up and cleaned the insides including the buttons. There was no fluid spilled into the keyboard itself. No sign of anything on the circuit board either. Could this be a faulty circuit board that needs replacing? Thanking you in advance for any help given. Denny.