Hi Bert,
I recommend calling up the internal Test Program of the CVP-609 and running test #052 Touch Screen Check there. The touch screen is also calibrated during this test. Then you run test #054 Test Exit to exit the Test Program. Maybe you are lucky and that solves the problem.
If not, you could go back to the Test Program and do a full Factory Reset. (However, this will delete all user data, including the entire User drive!)
To carry out the reset, first run test #053 Factory Set. Note: After performing this Factory Set function, be sure to execute #054 Test Exit. At this time, do not turn off the power until “GrandPiano1” appears on the LCD display.
If the problem is not solved even by a full Factory Reset, only Yamaha Service can help you.
Important: In order to run the Test Program, you absolutely need the corresponding service documents. You are welcome to contact me via PM (Personal Message), then I will send you detailed information.
Best regards,
Chris