 you don't really want to break the surface of the wood because it will create splinters. If you break the surface of a composite deck, it kind of, in the heat of the day, will kind of grow up around that screw a little bit. So it's interesting that it's backing out, but I'd try it in a corner. If you've got a screw that's backing out, just tighten it down until you get it flush, and I don't think you'll have too much to worry about.