I heave a four year old bis tradition CE. Until recently I have been able to completely close my damper and have a hot, slow, clean burning fire that will last a solid six + hours. This year however it seems I’m sucking in Air from somewhere. Once my fire is burning well, I close my damper and it obviously reduces the air flow but not like it used to. It results in shorter burn times for me. Am I able to adjust my damper? Could it be the seal around the door? It looks like it is in good shape. Just seeing if anyone has any ideas. Thanks