The WordPress bug affects websites sitemaps that are generated by the WordPress core. The bug affects websites that have so many pages that they need more than one XML site map. According to the bug ...

If I visit /wp-sitemap.xml, there is an url in the list: /wp-sitemap-taxonomies-post_tag-1.xml If I click on it, 404 page comes in. All other links are working (like: /wp-sitemap-taxonomies-category-1 ...