503 Service Unavailable after 60 seconds Apache Symfony (in certain features only)

I currently face an issue in a Symfony 3.4 application, in one of its features which loads history of some data (a lot of data actually which dates from 2017). When trying to access the history feature, the GET HTTP request keeps loading for 60 seconds exactly, then a 503 service unavailable shows up, same issue happens in other features that loads big number of data. Checked the logs, application logs and server (Apache) logs, only Apache logs shows 503 code with no details. I suspected the php.ini configuration, and changed values of max_execution_time to -1 and memory_limit to 2048M, but still the GET HTTP request terminates after 60 seconds exactly. I also use php-fpm and checked the www.conf and it doesn't have anything that overrides the values of php.ini. I even added request_terminate_timeout = 600s to only see if the value will be taken into consideration but still the same issue, GET HTTP request of the history terminates exactly after 60 seconds of loading (waiting). I make sure to restart php-fpm and httpd (Apache) after the changes in the configuration file. The os system is **Redhat**, Database server is working fine, since I can access other data in other features. Expected behavior: I expected at least the GET HTTP request to keep loading for more than 60 seconds, other than that it means I still didn't find the correct parameter. Logs from ssl_access_log: ip - - date "GET /p/a/h HTTP/1.1" 503 299