On dewiki the imagelinks tables contains values like "Bild:<imagename>" at il_to although the page source correctly contains [[Datei:<imagename>]]. The image namespace prefix must not be add to the il_to value.
If you are doing a null edit using index.php the wrong entry is deleted. But we made a null edit on all pages and there are some few news ones every day.
You can find examples on the missing file reported created twice a week on http://de.wikipedia.org/wiki/Wikipedia:Redaktion_Bilder/Arbeitsliste_Fehlende_Bilder if you are searching for "Datei:Bild:"
I don't know the reason, but perhaps there is a single not updated squid or an old mantanace scripts that run on wmf.
Version: unspecified
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=32171