@melanie_d My patch is in the wp-api-v2-menus.php file. The existing method for walking the nav tree inherently causes the error, so I had to rewrite with another strategy. It’s in get_menu_location(). Double-check on the diffs in case I’m forgetting something.
I’m a WordPress newbie (though not new to PHP), so consider my code suspect ?? I thought I might write a new set of menu routes for my own purposes as it takes several GETs on these endpoints to build a usable tree of nav menu items. Let me know if you’d like to collaborate via a fork of this one.