I'm a a/c contractor and have had several 9620 heat pump t stats to lock out and show ERR on the display. When this happens the emg heat red light is on and the heat will lock on and the homeowner cant turn it off at the tstat, the only way they can turn it off is at the breaker. You can push a reset button and it will reset. I was just wondering if any other contractors out there are homeowners have had the same problem?