I just saw a server error message at https://serverfault.com/error?aspxerrorpath=/questions/520272/php-fpm-performing-worse-than-mod-php.
The large image on that page is broken as it's being served from https://sstatic.net/serverfault/img/error-missile-command.jpg but the certificate is valid for *.stackexchange.com
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This is possibly related to Going to any question on the site brings an error page.