Bosch glass top stove with touch controls keeps flashing- "E","r" & "2" whenever I put a pan on the stove top or when I turn the temperature down if I have been cooking. I have tried changing the temperature and turning off. Tapping start button once or twice does not restore function. It eventually stops flashing but it can take half an hour or so. I cannot operate the cooktop at all during this time. I have misplaced my manual.