I have a totaline P474-1100REC receiver. It was working perfectly, matched to a totaline wireless digital thermostat: P474-1100RF. Now, when I lower the temperature from the thermostat, my furnace won't shut off. The signal to turn on the furnace is sent from the thermostat as indicated by the light flash on the front of the thermostat and received, as indicated by the "heat" indicator on the face of the receiver, and the furnace turns on as usual. When I lower the temperature, the signal is sent and received but the furnace does not shut off. Amazingly, when I remove the cover from the receiver, after about 2 minutes, the furnace DOES shut off as it used to by just lowering the thermostat. Any suggestions?