WP 5.8 and 5.8.1
faultCode0faultStringFatal error:Uncaught Exception: Supplied nav_menu_item value missing property: status in C:\…..\wp-includes\customize\class-wp-customize-nav-menu-item-setting.php:183 Stack trace: #0
Solution:
Open add-descendants-as-submenu-items.php line 309 after $child->menu_order = $menu_order;
add
$child->status = $item->post_status;
if your missing property is status otherwise
$child->yourmissingproperty = $item->missingproperty;