Portfolio or other special page links not highlighted as active or stuck on active

To work around this, you may give the menu item a custom class in Appearance → Menus.

1. Click Screen Options in the upper-right of the Menus page and ensure CSS Classes box is checked.
   
2. Expand the menu item that is misbehaving and enter a custom class name in the CSS Classes field.
   
3. In the Custom CSS, add your style like this:

   .my-active-link  a .class:active { color: #f00; background: #000000; font-weight: bold; }

4. Replace the properties/values with your desired styles.