My problem is still not solved. After debugging, I found:
on line https://github.com/Rackster/ispconfi...in.inc.php#L54
I'm calling the method - and I get a FATAL Error, method not found.
It looks like it's called in a static scope (nginx_reverse_proxy_plugin::cert_helper()) - so I tried making the method static -> no success.
What could be wrong there? This is new since 18.104.22.168
Thanks for hints & help