You helped me to find a bug in admin menu access add-on. Thanks. I will develop a fix next week as I return home from a short trip. It will take some time for testing before I can to publish the update.
A quick workaround is to add ‘edit_portfolios’ capability to the role and block all ‘Portrolio’ menu items via the same admin menu access add-on. I did this at your site and user with ‘Klant’ role does not have access to the ‘Portfolio’ menu.