A lot of templates mistakes
I discovered a lot of mistakes on path vars:
In file:
/usr/local/ispconfig/server/conf/vhost.conf.master
The "php_admin_value upload_tmp_dir and session.save_path" folder is set to document_root, but should be set to web_basedir The FastCgiExternalServer path is also set to document_root and not to web_basedir.
The php_admin_value from mod_php and php-fpm is different, but should be the same:
sendmail_path is missed in php_fpm_pool.conf.master and also the tmpl var 'domain' get not resolved (a template system should provide all vars to all templates)
Also session.save_path and upload_tmp_dir are only set when enable_php_open_basedir is enabled... with mod_php it get set every time.
Hope that this can be fixed, I fixed it for me with a copy to conf-custom.