I've seen similar situations, but never in bulk and not with adult sites. Basically what's happening is somehow a domain (or multiple) are linking to your site with inaccurate URLs. When bots crawling those sites find the links pointing to yours, they obviously hit a 404 page which triggers the error in Search Console.
Unfortunately, there's not too much you can do about this, as people (or automated spam programs) can create a link to any site and any time. You could disavow links from those sites, which might help from an SEO perspective, but it won't prevent the errors from showing up in your Crawl Error report.