I've got a 3 year old Harman Absolute43 pellet stove that's been acting up this winter with a number of issues, but most urgent is the recent spate of ash bin fires. The stove is set to it's thermostat, but once it hits the desired temp, the auger continues to feed pellets into the firebox, overheating the place and eventually spilling flaming pellets into the bin, which pile up and burn like crazy. The fan eventually shuts off, and smoke starts to leak into the house while the bin smolders...Any ideas? Everything was cleaned 3 weeks ago, including the exhaust sensor.