Modal does not show

Hi
I want to link Joomla menue items from linky map areas, this works fine when I use the action "Open URL" but when I choose the action "Modal" it does not show up. Have tried it in latest Chrome and Firefox, same result.

You can see it here:
http://stirnimann.brandserver.ch/unternehmen#aussendienst-nach-regionen-mobilkrane

Is there a bug in linky map modal-action?

Thanks
Chris