Dropdown menu multiple levels

Hi,

Can anyone help me with this issue? I'm using a Superfish multi level menu but when I resize the screen and the menu changes from normal to dropdown, I can only see the first and second level of the menu. Further levels are not displayed in the dropdown menu.

(In case of multiple levels, I have no links to the parent item(s) (path=) so only the child items have a URL link.)

Thanks,
Steven