On Christipediawiki the page "Christipedia:Info", last time changed on april 3th, has vanished. Instead an empty page entitled "Speciaal:Badtitle:NS4:Info" appeared.
In the same way, the subpage "Christipedia:Info/Inkomsten en uitgaven" disappeared and instead an empty page "Speciaal:Badtitle:NS4:Info/Inkomsten en uitgaven" appeared.
All this can be seen on the page Recent changes
Perhaps the bad title error has something to do with the issue mentioned here: https://www.mediawiki.org/wiki/Thread:Extension_talk:OpenID/https_site_and_Special:Badtitle
It also turned out that the connection with inserted images on all pages is lost, though the images are still there on the server and can be found by the search function.