I use the INF driver, cams are shown in device manager as "libusb-win32 devices".
Cams are running on battery power.
Serial numbers are shown.
Obviously the hub is the problem. When connecting the cams directly to the mainboard USB ports, everything works fine.
I use a 7 port hub like this:

Every single port works fine, even without external power supply.
Is there a special kind of USB hubs required / not suitable?