Starting with RHEL-8, httpd work in threaded mode (event MPM) and use php-fpm for better performance and security.
In RHEL-8 mod_php is still provided, and it is removed in RHEL-9
mod_php is only available in old worker mode (prefork MPM), so if you switch back to it, mod_php will be used.
Check /etc/httpd/conf.modules.d/00-mpm.conf to select the proper MPM
LoadModule mpm_prefork_module modules/mod_mpm_prefork.so
Also check /etc/httpd/conf.modules.d/10-php.conf to enable mod_php
LoadModule php7_module modules/libphp7.so
I believe the PHP-FPM is causing issues
I recommend you investigate these issues rather than trying to workaround them switching to old deprecated way.