Hi My PX 850 is very out of tune. I suspect it is my daughter hitting the keys randomly with operation lock off. I have tried turning backup and operation locks off (long beep on both) and restarting the keyboard, but it is still out of tune. I thought that turning backup off meant that all settings were forgotten on restart, but it doesn't seem to work. Is there some other way I can factory reset the keyboard? If not, and anyway, is it possible to zero the tuning without having to retune it incrementally? Thanks