Virtual Sub Client Setting

Hello

Urbackup 2.1.20
I installed the client no tray 2.1.17 on windows 2008 R2 server.

The virtual sub client names function is very interesting and allows me to differentiate each user account with SERVER [User].
When I create a virtual sub client, it’s ok, the backup starts but when I add another virtual sub client, the first is doubled and so on. in addition this disables the first client.
I would like to understand why.

Thank to help me

S.C