If it is coming from the wood then maybe washing it down with a bleach might work. I would use bleach let it sit a few minutes then rinse it throughly. Then use a bleach solution and let it dry. Then rinse it off. Let it dry throughly and then paint the wood with mildew resitant paint. Don’t forget to do the door as well as all the walls and cupboards. I would also do the suggestion for cleaning the sheets stated in the previous entry. Both combined should remove the odor.