I found in rs.miraheze.org, sometimes the MediaWiki-namespaced pages are occasionally ignored, and sometimes work normally. For example:
- The sidebar sometimes displays as default, ignoring the page MediaWiki:Sidebar, and sometimes displays normally according to that page.
- Viewing a module page (for example Module:Navbox), the documentation sometimes displays as default, ignoring the page MediaWiki:Scribunto-doc-page-show, and sometimes displays normally using the doc template used in that page.
- The sitenotice sometimes doesn't show, and sometimes show as in the page MediaWiki:Sitenotice.
This issue has been existing for months and I can't find a solution.
See also this post.
If you repeatedly refresh or purge a page, you may find it sometimes normal and sometimes abnormal, seemingly randomly.