We have a Whitfield Optima 3 Insert, 10 years old... This year it will only run in low mode. It will run endlessly in low mode, but a little too low. In medium or high it will shut itself down in 15 to 20 minutes and never achieves a high flame. I can hear the auger motor... Honestly the flame is higher in low. I've cleaned it throughly, as well as the exhaust/flu... My gut tells me the auger motor is failing... Anyone had this problem before... Before I buy an auger motor I don't need...