I have a Mt. Vernon AE insert and I am having trouble with the thermostat not working properly. From time to time the unit just does not restart for some reason. Serveral times was after the hopper ran out and the "min firepot temp" prompt has come up and some other times was when we refilled the hopper before the stove runs out. The only way to restart the stove is to unplug and replug the unit to force an autoclean cycle. Any ideas on this?