when upgrading to 5.4.1 i encountered an issue where i started getting error 500's part way through the upgrade which then broke the upgrade (and nagios in general)
looking at the httpd logs i could see that PHPMailerAutoload.php was giving a permission denied error...
looking at that file its ownership was root instead of nagios like it should have been
changing the ownership to nagios by running chown nagios.nagios PHPMailerAutoload.php fixed the issue however then running the upgrade from the website still wouldnt work
i then had to run /usr/local/nagiosxi/scripts/upgrade_to_latest.sh which reran the upgrade and finished without issues
Just incase anyone else hits this same issue
