Why it matters
Sitemaps should only contain canonical, live URLs; 404s and redirects waste crawl budget and erode trust in the sitemap. Over 5% of sampled URLs failing is a scoring gate.
How to fix it
Generate the sitemap from the same data source as the routes, and list final URLs (no redirects, correct trailing-slash form).
References
More seo rules
void seo reports 60 rules in this category. What search engines need from the raw response: status codes, titles and descriptions in <head>, self-referencing canonicals, one h1, crawlable links, Open Graph, icons, robots.txt and a sitemap with real dates.
robots-sitemap-directiverobots.txt has no absolute Sitemap: linesitemap-missingNo reachable sitemapsitemap-invalidSitemap isn't valid sitemap XML or exceeds protocol limitssitemap-url-invalidSitemap <loc> is relative or on another hostsitemap-lastmod<lastmod> invalid, in the future, or identical across entriessitemap-url-not-indexableSitemap lists noindex, robots-blocked or non-canonical URLsduplicate-titleMultiple pages share the same <title>duplicate-descriptionMultiple pages share the same meta description