Server issues after switching to PHP-FPM

My server was running great for years before I switched PHP execution from mod_php in apache (with an nginx reverse proxy) to PHP-FPM in nginx. My website itself doesn’t use PHP except for tracking visitors via piwik/piwik.php. Since making the switch, my website monitor has been reporting some very short periods of downtime.

Could PHP-FPM be having intermittent issues executing piwik/piwik.php?

Piwik works perfectly on nginx and php-fpm so this must be a server configuration issue

Any tips for getting the config right as it pertains to this sort of thing?

ask sysadmin?