503 error on user websites caused by CageFS

Check the logs
tail /var/log/apache2/stderr.log
Fri Apr 29 12:32:02 2022 (95855): Fatal Error Unable to create lock file: Bad file descriptor (9)

To fix the issue follow this guide: Apache: Fatal Error Unable to create lock file: Bad file descriptor (9)
Disable CsageFS for that user:
/usr/sbin/cagefsctl --disable $username
and enable it back:
/usr/sbin/cagefsctl --enable $username


![node[175421]: pthread_create: Resource temporarily unavailable 2023 08 28 12 15 - node[175421]: pthread_create: Resource temporarily unavailable](https://i0.wp.com/administrator.pejcic.rs/wp-content/uploads/2023/08/2023-08-28_12-15.png?resize=344%2C194&ssl=1)
