We purchased a Harman Accentra Insert back in 2013. We love it. However, last winter we noticed that the feeder was calling for too many pellets and we'd constantly be dumping the ash tray with partially burned pellets. We've always done thorough cleanings, including the heat probe and having the chimney cleaned regularly. It's like it's calling for too much heat or something. Any suggestions on hot to troubleshoot so we don't waste so many pellets?