Chony.

An intermittent problem, such as an occasional flickering of the screen is difficult to diagnose at best. It's quite possible that one of the connectors that connects the display to the keyboard's mother board worked loose during shipping. If you have a local, Authorized Yamaha Repair Center that has a good reputation and quick turnaround time, I would have them check it out for you and mention the possibility of a loose connector. This can happen with any complex electronic equipment that has multiple PC boards. It happens with laptop computer all the time.

Hopefully, this will solve your problem,

Gary