Yes you are right. I did sucessfully mirror the Schätztheorie.html page, but
the  link in the left side menu to Schätztheorie.html refers to
Schätztheorie.html.  

A solution is to manually rename the mirrored file:

from:
<file://mars.wiwi.hu-berlin.de/mediawiki/mmstat_de/index.php/Schätztheorie.html>

to: 
<file://mars.wiwi.hu-berlin.de/mediawiki/mmstat_de/index.php/Schätztheorie.html>

I'm afraid that's the best solution, I can come up with. 

- Bo Hovgaard Thomasen