I've had my serenity stove operating about four months-It recently started a knocking noise during the auger cycle--cleaned out the pellet holding tank--manually checked the auger--it does have a little play right to left , but the set screw is definitely tight on the shaft coupling. cant feel any real vibration or knocking on the motor or gear box---Has anyone had a similar experience with their Serenity? Let me know==thanks everyone--Lucky1