I bought this stove used. It ran great for a month. After doing a 2nd full cleaning the problem began. The unit will start up normally. But then Seems like it's getting too much air. As it goes the fire will die out and as pellets drop it will smoke up and refire burn like to much air again and repeat until it's just out. The damper is closed the whole time. If i open it it is wild and blows out..... idk whats wrong with it.