If your containers suddenly stop working due to “Too Many Open Files”, you can adjust that with the DefaultLimitNOFILE on the SystemD configuration files /etc/systemd/user.conf and /etc/systemd/system.conf. Depending your system setup, you may need to adjust both.
In my case I have, DefaultLimitNOFILE=16384:65535 for the user.conf file and DefaultLimitNOFILE=65535:524288 for the system.conf file.
Reboot your system after adjusting this setting. After that, you will also be able to tweak value between the soft and hard limits using the ulimit command.
