@manilx We recently upgraded our Koji build system. This may have caused disruptions in this recent update release yesterday, where an XML file was generated multiple times. This has now been fixed and should not happen again. This may explain the issue encountered this time, particularly with the notification of updates via XO.
Note that normally yum metadata expires after a few hours and so it should normally return to normal on its own.
That's the reason, then. The update will update files on the disk, not on what's running in memory, so after updates you must reboot to actually use those updates