I have a Calumet changing box which has two curtains with zips. The zip on the inner curtain just came off. The box is only a few months old and I don't get how this happened. Anyway, I tried to fix it and I couldn't. My question is should I still worry about stray light since it has a first curtain with zip(even though this is silver in colour) and the second curtain despite having a broken zip and can't close it is matt black and it doesn't open much?