Transferring virtual server to another VirtualMin host doesn't recreate additional ftp users

I have observed this in different occasions. Right now I’m transferring a lot of virtual servers from one server to another. Buth are VirtualMin 6.02 GPL, running on CentOS 6 systems.
The transfer finishes without error, but all additions FTP users (created with “Edit Users” => “Add a website FTP access users”) are not recreated on the target system.

Has anyone observed this before? Is this a known problem?