I found the below in apache log.
require_once(/home/XXXX/public_html/om/gtdtl/vendor/composer/autoload_real.php): failed to open stream: No such file or directory in /home/XXXX/public_html/om/gtdtl/vendor/autoload.php on line 5, referer: /gtdtl/transactionsadd.php
[php7:error] [pid 5790] [client 192.168.100.4:51959] PHP Fatal error: require_once(): Failed opening required ‘/home/XXXX/public_html/om/gtdtl/vendor/composer/autoload_real.php’ (include_path=‘.:/usr/share/php’) in /home/XXXX/public_html/om/gtdtl/vendor/autoload.php on line 5, referer: <>/gtdtl/transactionsadd.php
[Fri Mar 27 16:17:47.994234 2020] [php7:warn] [pid 14805] [client 192.168.100.4:51960] PHP Warning: require(/home/XXXX/public_html/om/gtdtl/vendor/composer/…/symfony/polyfill-mbstring/bootstrap.php): failed to open stream: No such file or directory in /home/XXXX/public_html/om/gtdtl/vendor/composer/autoload_real.php on line 66