ShiftyByte

Yes, I a pretty sure because of this message in the log: Another app is currently holding the xtables lock. Perhaps you want to use the -w option? And this article: https://utcc.utoronto.ca/~cks/space/blog/linux/IptablesWOptionFumbles And the fact that starting the failed service post boot works. (So it's not a permanent failure, it just fails when its run automatically at boot) systemctl start webmin-ip6tables.service

I'm not sure how this is connected. I am talking about systemd service called webmin-iptables.service I could not locate it on the github, maybe i'm misunderstanding who is responsible for this file.

webmin-iptables.service or webmin-ip6tables.service fail at boot.