I have found this in several places. Please let me know if this is a real problem or just my imagination.
We have several wiki areas for different languages.
It looks like that images that are uploaded into non-english wikis override files in the main one, if they have the same name.
And because the change is actually made to the non-english wiki, it is impossible to track back why the image had changed all of a sudden. No change is shown either in the history of the "english" page, or in the history of the "english" image.
For example: http://docs.moodle.org/en/Settings. You can notice that this is an image in Russian language and it was originally uploaded into a wiki in Russian.
The same happened to this page: http://docs.moodle.org/en/Metacourses
First it was in English, then as a miracle in Chinese (http://docs.moodle.org/en/index.php?title=Metacourses&oldid=6137), then in Russian (http://docs.moodle.org/en/index.php?title=Metacourses&oldid=13617), and then I have uploaded my own file in English.
You can see from the page comments: http://docs.moodle.org/en/Talk:Metacourses that people got confused and there we no logs to track back image changes.
Does anyone know why this happens and how can we avoid it? (I assume that having different filenames can help, but it this will be a quick fix, not a solution).