I got a second-hand Dgx 630. I was amazed by the sounds and keyboard action. I just noticed that there was some problem with the buttons. For example, pressing dual on/off plays the demo sound. Pressing the black button for portable grand takes to 000 sound instead of default piano sound. Additionally, Dual on/off only works if I press the exit button along with it. It is strange but wanted to know any solution. Does it need any driver update or something similar?