safesearch actually works exactly how it's supposed to, and it can't really work any better.
there will always be that one image with tits that isn't tagged/reported as research, so it'll get through. up until someone reports it.
technology hasn't gone so far as to detect tits in an image, which it has to rely on what users don't want to see in order to improve it's filtering. to do this, users have to eventually come upon that one image with tits.