I can't quite see that these errors are directly related to X3 / PHP code. There are no php-specific errors in the warning, and nothing we are calling from X3. I have checked update-notes about PHP 7.3, which are not drastically different from PHP 7.2, and there isn't anything that outdates X3 PHP code.
I can't exclude that it is X3-related, but unless I can reproduce the issue, or a traceable PHP error is logged, it's hard to diagnose.
hstruck wrote:AH01067: Failed to read FastCGI header
AH01075: Error dispatching request to:
I found some links:
https://serverpilot.io/docs/error-faile ... cgi-header
https://talk.plesk.com/threads/errors-a ... 75.348426/
We also use FPM/FastCGI on our servers: