After struggling with trying to upgrade my 7.5.2 installation to 7.5.3, I finally succeeded but there were a few gotchas worth noting, expecially if you're having mysql errors all over the place. I upgraded via the manual method. Most important was to make sure that mysql and named is running at the time. Don't shut down these daemons prior to an upgrade. Using "/etc/init.d/psa stopall" will stop these daemons so you'll need to restart them before upgrading. I'm running on CentOS 3.4 and prior to 7.5.3, I was running the RHEL version of Plesk. So when 7.5.3 came out with CentOS 3.3 support, I tried crossgrading to the CentOS 3.3 version of 7.5.3 without problems. The only thing you need to do is add a "--force" parameter to the upgrade command (eg rpm -U --force *.rpm) because rpm thinks the rhel packages are newer. That's about it!