The timing on this never seems to fail. I can have a fire going all day long, but as soon as I lay down to go to sleep, the door on the air intake begins to open and closed making a tapping sound that would put any leaky faucet to shame. If I open the intake a bit to allow more air in just a bit, it will stop, but will often begin again (of course, right before I fall asleep). If I open the door too much, it often allows too much air in causing the stove to over-fire (which is something I'd just assume not sleep though). Its a wonderwood wood stove similar to this one (http://www.usstovefactorydirect.com/images/woodstove/us2941.gif) but I am not sure of it's actual model type (as I am not at home at the moment). Any clue as to what causes this, and how I can go about fixing it?