I disabled (User_active) your mirror in MirrorManager since it seems to
be broken for a few weeks. The crawler reports that it is failing since
at least 2014-12-24 and the last update seems to be even longer ago.
As you are also running report_mirror the mirror is still marked as up
to date and clients are redirected to your mirror and getting 404s.
In addition your rsync configuration seems to be broken:
$ rsync mirror.slu.cz::fedora/
CentOS mirror at Silesian university in Opava
@ERROR: failed to open lock file
rsync error: error starting client-server protocol (code 5) at main.c(1635) [Receiver=3.1.1]
Once the mirror is fixed please re-enable your mirror in MirrorManager
or let me know and I can enable it for you again.
Thanks.
Adrian