conditional menu not working

I cannot change any of the settings for the existing items in the main menu: neither the choice between public or logged in users, nor for specific roles.
When I add a new menu item, it will stay ‘public’, so no changes possible here too.

I disabled all plugins, switched to standard theme, made sure there are no ompatibility issues with my theme (does not use the wp_nav_menu_item_custom_field with 4 arguments instead of 5).

I’m tempted but hesitating to roll back to a previous version, keep hoping for a well working update.

The page I need help with: [log in to see the link]