我有一个运行lemp堆栈的服务器，它承载着各种各样的网站。在夜间，所有站点都被关闭，并显示消息“502坏网关”。我遵循错误流，得出结论，php7.4-fpm是问题所在。我需要帮助找出如何解决下面的错误。
注意：夜间，未对系统进行任何更新或更改

● php7.4-fpm.service - The PHP 7.4 FastCGI Process Manager
     Loaded: loaded (/lib/systemd/system/php7.4-fpm.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Tue 2021-07-27 09:35:38 CEST; 7s ago
       Docs: man:php-fpm7.4(8)
    Process: 1561620 ExecStart=/usr/sbin/php-fpm7.4 --nodaemonize --fpm-config /etc/php/7.4/fpm/php-fpm.conf (code=exited, status=78)
    Process: 1561621 ExecStopPost=/usr/lib/php/php-fpm-socket-helper remove /run/php/php-fpm.sock /etc/php/7.4/fpm/pool.d/www.conf 74 (code=exited, status=0/SUCCESS)
   Main PID: 1561620 (code=exited, status=78)

Jul 27 09:35:38 Ubuntu-2010-groovy-64-minimal systemd[1]: Starting The PHP 7.4 FastCGI Process Manager...
Jul 27 09:35:38 Ubuntu-2010-groovy-64-minimal php-fpm7.4[1561620]: [27-Jul-2021 09:35:38] ERROR: [/etc/php/7.4/fpm/php-fpm.conf:98] value is NULL for a ZEND_INI_PARSER_ENTRY
Jul 27 09:35:38 Ubuntu-2010-groovy-64-minimal php-fpm7.4[1561620]: [27-Jul-2021 09:35:38] ERROR: failed to load configuration file '/etc/php/7.4/fpm/php-fpm.conf'
Jul 27 09:35:38 Ubuntu-2010-groovy-64-minimal php-fpm7.4[1561620]: [27-Jul-2021 09:35:38] ERROR: FPM initialization failed
Jul 27 09:35:38 Ubuntu-2010-groovy-64-minimal systemd[1]: php7.4-fpm.service: Main process exited, code=exited, status=78/CONFIG
Jul 27 09:35:38 Ubuntu-2010-groovy-64-minimal systemd[1]: php7.4-fpm.service: Failed with result 'exit-code'.
Jul 27 09:35:38 Ubuntu-2010-groovy-64-minimal systemd[1]: Failed to start The PHP 7.4 FastCGI Process Manager.

我很感激你能有任何想法！