I too am having mildew on allof my medela freestyle shields no matter how well I wash them. This is the third child that I have nursed and never had this issue with previous pumps (both medela's), however, I noticed that the freestyle shields/parts have a different (new?) material that I haven't seen on other medela shields. The mildew is only on the beige/yellow pieces of the shield which makes me think that it is an issue with the material being a good medium for mildew growth. I'm going to ask the medela company about it, because I think that even if I buy more parts they will eventually just get mold on them too. Hope this helps....