well i cant promise this will help but we had very similar problems happen with digital pentranic chassis,what would happen is from time to time the chassis would suffer from a static zap which would reset the presets thus causing your exact problems,no brightness etc making the engineer think that the chassis was at fault-in fact there was a set up routine using a pot-what you had to do was hold the adjustment control on during power up thus giving you an extended menu with a save option,only on this menu could save your brightness controls etc-now i dont know about your chassis but i bet you a quid its something on that line.please tell me how you access the adjustments menu.unfortunatly many industry techs are about as helpful as a chocolate tea cup.