Have you tried a factory reset? Hold the 'A' button in while turning on the power and hold it in for 5-8 seconds. Note this will delete any User presets you have created, so back them up on a computer using an FBV Mk11 controller first.
Does it exhibit this problem no matter what preset you are using, and on manual settings, as well?
If the factory reset does not work, you will need to bring it to a factory authorized service center for evaluation and repair.