After upgrading VirtualMin this Monday/Tuesday on 7-8 different servers, every server had proftpd disabled as this is something I do on every server I have VM running.
However, proftpd enabled after it restarted the VM service when the upgrade was complete. My firewall configuration has port 21 blocked, so this was not an issue. But the proftpd service should not be started after upgrading the VM packages.
This appears to be a bug in my opinion.