Using the factory 3 preset, I hold down the tune foot switch to allow the unit to set the key. I have also held down the tune foot switch as I play on Preset 3 so that it tracks the key. When I do this, all of the other presets go away. Turning the control knobs has no effect. Only preset 2 and 3 function. If I cycle power, no change. If I turn the unit off for approx. 5 minutes, then it goes back to normal. This can be repeated. Any Ideas???