sites without https give someone else's content.
If at least one site creates https keys, then all other sites that do not have https begin to give https content to the site where the keys are registered. HTTP connection is different from HTTPS since HTTP referer is sent after connection. Wherein HTTP referer is not readable, but by taking the nearest keys, it is the nearest! Those that will be closer alphabetically!
Create at least 1 sites with https
environment in any versions of ispconfig!
ln -s /etc/apache2/sites-available/default-ssl.conf /etc/apache2/sites-enabled/1.conf
Partial solution of the problem, put the first 1.conf file, since it goes first and when there are no keys, it comes across first, you understand this crooked solution.
The right decision is to create https keys for each site by default, and if the parela is disabled, https then document root "/var/www/html/ssl" if SSL is enabled, then change document roots to real. There is no other way! In any case, the site will be accessible via https!