How to find what is causing the Internal Server Error?

Question

PHP

Score. When entering the admin panel Internal Server Error.
max_execution_time - 30 sec. (increase is not an option because you need to find the cause of the error)
In the error log:
FastCGI: comm with server "/fcgi-bin-php5.6-fpm-domain" aborted: idle timeout (30 sec)
FastCGI: incomplete headers ( 0 bytes) received from server "/fcgi-bin-php5.6-fpm-domain" Looked
in DB in SHOW FULL PROCESSLIST, there were about 20+ sleep processes, tried to end everything.
I am 99% sure that the problems can be fixed if you reboot the server. But you need to find the reason, because. this is not the first time this has happened.
Is there any way to find what and where is causing this error?

Answer 1

Is there any way to find what and where is causing this error?

Look at other logs, namely web server logs (apache, nginx), system logs (systemctl and / or syslog)
If the error is due to a timeout, then there is no other solution but to increase the script time or reduce the script execution time, but then you need to debug the web project code.