Run the following commands and check the output:
$ sudo cat /etc/cpupdate.conf
$ sudo cat /usr/local/cpanel/version
$ sudo cat /var/cpanel/updatelogs/update.$$$.log
replace "update.$$$.log" with the most recent update log where the update failed.
Run the following commands and check the output:
$ sudo /usr/local/cpanel/scripts/find_outdated_services
Then try rebuilding the RPM database to see if that helps: "WHM Home » Software » Rebuild RPM Database"
You can also try running this command manually to see if it continues to fail, and to verify the failure message:
$ sudo /usr/local/cpanel/scripts/post_sync_cleanup
If nothing works, force another cPanel update with the "/scripts/upcp --force" command.
If that also didn't work, then:
$ sudo yum clean all
$ sudo yum update