Strange behaviour when creating websites which are not working until restarting apache

Hi, I'm experiencing a very strange behaviour on my new setup of ISPConfig 3.1.11. It's running inside a Docker container created by jerob (I'm using a custom jerob/docker-ispconfig image edited to support pure-ftpd on OpenVZ).
As far as I can tell, I can't create a working website, since every one I create gets marked as an "error". ISP says that the creation has gone well, but as soon as I look into /etc/apache2/sites-available, I can only see vhosts with an .err estension.

At the beginning I was very sure it was an SSL related problem, but then I figured out that the website works if I stop apache from running, copying the .err vhost content into the .vhost real file and restarting apache2. This keeps working until I go to change my website configuration, in that cose something under the hood occurs, and ISPConfig marks my vhost as an .err file again.

Any suggestions?

 

Reason for Apache restart failure: /bin/systemctl: line 4: /etc/init.d/apache2.service: No such file or directory

Apache did not restart after the configuration change for website officinademarzo.it. Reverting the configuration. Saved non-working config as /etc/apache2/sites-available/officinademarzo.it.vhost.err

Seems like systemctl isn't able to start apache2.service. If I execute manually
systemctl restart apache2.service, the command line prints out
/bin/systemctl: line 4: /etc/init.d/apache2.service: No such file or directory

but if I execute manually systemctl restart apache2, it works like a charm
[....] Restarting Apache httpd web server: apache2AH00548: NameVirtualHost has no effect and will be removed in the next release /etc/apache2/sites-enabled/000-ispconfig.conf:73
AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
. ok