Backup symlink folder permissions wrong - pre 22.214.171.124
Any ISPConfig installation pre version 126.96.36.199 has the wrong permissions for the /var/backup folder, so the website smylink /backup folder does not work when users FTP into their site, getting permission denied when changing to /backup symlink folder.
Running this fixes the problem: chmod 755 /var/backup
Originally a pre 188.8.131.52 version was installed, where this was an issue. Then upgraded to 184.108.40.206, but this didnt fix the bug.