Some users not shown in CB

Hi,
when I look at my CG user management I don't see all my users.

The users that are not shown are all users that were created through the standard user management.

How can I add those to the CB User manager?

It turns out that those users are not shown because they belong to a custom group.

Now this brings me to the question: why are users belonging to a custom group not shown in the user manager?

Workaround is to set those users as members of both their custom group, and the parent (in this case it was "registered")