Delete Hardware Switch

Once a physical interface like internal1 became a member of hard/soft switch interface like internal, you wouldn't be able to bind a vlan interface to the physical interface. You can only bind it to the parent interface. If you want to bind a vlan to only one physical interface, you have to separate it from the parent interface. If you want, you can have only one member under a hard switch interface(virtual-switch in CLI) like internal, or a soft switch.

I finally deleted "internal" hardware Switch. After that the two physical interface of the hardware switch turned into independent physical interfaces.

Fortigates 60D need at least two physical interfaces per Hardware switch.

Thanks