Login to the dev wiki broken?
When you view the development wiki (which is not publicly accessible) and click the "Login" link, you are redirected to typo3.org, but to the 404 page.
The reason is Realurl. Realurl can only resolve paths, which have at least been generated once. The paths to the SSO apps are generated here: typo3.org/my-account/sso/
However, the dev wiki page is not in the menu, so it is not displayed and so the URL is not generated. Always when someone flushes the complete Realurl cache, the login breaks.
The solution is to make the page show up in the menu, open the page and hide it again.