Hello mirror team!
While searching for mirrors on https://admin.fedoraproject.org/mirrormanager/ for Fedora 26 I stumbled across some out-of-sync mirrors:
http://ftp.uma.es/mirror/fedora/linux/updates only contains updates up to Fedora 25.
http://ftp.udl.es/pub/fedora/linux/updates only contains updates up to Fedora 23.
http://ftp.cica.es/fedora/linux/updates/26/x86_64/repodata contains updates for Fedora 26, but they are stuck at the state of the 4th of December 2017 - quite nasty from a security point of view.
It was recommended to me to report such mirrors on this list (https://forums.fedoraforum.org/showthread.php?317398-Fedora-Mirrors-and-keep...).
I hope it helps and that you can get them unstuck.
Best regards, Michael