I have a CT1950 Chronotherm Electronic Programmable Line Voltage Thermostat ~ 10 years old. The manual override stopped working a couple of weeks ago. I raise the temperature and it holds the new set point for about 5 minutes before it reverts to the pre-programed temperature for the period. I have tried resetting the unit using a paperclip and reprogramming the schedule but I am still having the same problem ?