Menu Items Not clickable

Dear Sirs,

I have an information website for Antiques, Art and Design.
For this site I use the theme Kahuna and the default menu.
This default menu is located above the header

In this menu are 6 groups with submenus up to 3 level deep
In the 3rd level are only 3 or 4 items that link to the appropriate page.
The corresponding pages of the following items will no longer be requested.

If you want to get the next page for example in the Puldown menu, nothing happens.
DESIGN VAN 1850 TOT NU
DESIGN TUSSEN 1850 EN 1910
ART NOUVEAU
HENRI VAN DE VELDE

https://antiekexperten.com/design-van-1850-tot-nu/design-tussen-1850-en-1910/art-nouveau/henri-van-de-velde/

I think there is a limitation for the number of item that is clickable in a submenu?
Can this be fixed by CSS or a other manner???
Please can you help me?

Karel Waegemans
https://antiekexperten.com

Website: antiekexperten.com