Carswell,
It sounds like you still have some leakage into the drum or the entry connection in the top of it. With the unit running, you need a smoke stick (incense stick, a cigarette or something similar) and move it carefully around the duct at the base of the cone, the fitting into the lid and around the edge of the lid where it meets at the top of the drum. If you are using a galvanized ash barrel, check the rivets where the handles attach as they may leak as well. Any leak will be evident with the smoke being sucked into the drum or connection at that point. Hope this helps.