Nginx not logging (restart needed)

We're running Nginx on a couple Ubuntu servers (16.04) and all in all everything is working fine. However after some time (few days) Nginx stops logging requests to the logs (/var/log/nginx/[host].log). If I restart Nginx logging resumes/starts back up. But pretty frustrating as I don't know exactly when logging stops and all in all, don't want to not be logging the traffic.

Thoughts on what could be causing this or how to fix?

Logrotate config:

/var/log/nginx/*.log {
    daily
    missingok
    rotate 14
    compress
    delaycompress
    notifempty
    create 0640 www-data adm
    sharedscripts
    prerotate
        if [ -d /etc/logrotate.d/httpd-prerotate ]; then \
            run-parts /etc/logrotate.d/httpd-prerotate; \
        fi \
    endscript
    postrotate
        invoke-rc.d nginx rotate >/dev/null 2>&1
    endscript
}