When clicking on a sub-menu toggle inside the primary navigation to open that menu, the element’s aria-expanded attribute is still set to false.
(here is a typical CSS selector for such a toggle: .moremenu .dropdown .dropdown-toggle)

Not only could this be an accessibility issue, fixing it would also make it easier to style opened menus.

It should be reproducible when setting custommenu to something like this:

Some Menu

-example a|https://example.org

Some Other Menu

-example b|https://example.org