Anyone know of reasons that the stove will stop feeding other than the pellets being too long? I have a Harmon XXV that will consistently shut down due to the pellets not feeding (4 times today alone). I mix up the hopper with my hand and it starts right back up. I have removed the plate in the back feed area and cleaned out ALOT of what looked like saw dust but it continues to do the same thing. Is there any where else I should clean?