Why my taxonomies are not working the hierarchal way on my custom posts?

Question

So, here's the deal, i have a custom post type and a custom taxonomy for it, both with hierarchy enabled. I register the 'categories' of the custom post type inside the taxonomy, following this template:

• Category
  • Child category
  • Second Child Category

But, when i save a custom post type inside one of the child categories, she cease being a child category, as in the following image:

Below is the code which is used to create both, taxonomy and custom post type:

$label = array(
    'name' => _x('Arquivos', 'post type general name'),
    'singular_name' => _x('Arquivo', 'post type singular name'),
    'add_new' => _x('Adicionar Arquivo', 'event'),
    'add_new_item' => __('Adicionar novo Arquivo'),
    'edit_item' => __('Editar Arquivo'),
    'new_item' => __('Novo Arquivo'),
    'view_item' => __('Ver Arquivo'),
    'search_items' => __('Procurar Arquivo'),
    'not_found' => __('Arquivo não encontrado'),
    'not_found_in_trash' => __('Arquivo não encontrado na lixeira')
);

$args = array(
    'labels' => $label,
    'public' => true,
    'publicly_queryable' => true,
    'show_ui' => true,
    'query_var' => true,
    'menu_icon' => 'dashicons-upload',
    'rewrite' => true,
    'capability_type' => 'post',
    'hierarchical' => true,
    'menu_position' => null,
    'supports' => array('title', 'editor'),
    'taxonomies' => Array('categorias_arquivos')
);

register_post_type('arquivos', $args);

register_taxonomy('categorias_arquivos', array('arquivos'), array(
    'hierarchical' => true,
    'label' => 'Categorias',
    'singular_label' => 'Categoria',
    'rewrite' => false)
);

register_taxonomy_for_object_type('categorias_arquivos', 'arquivos');

Answer 1

WordPress simply displays the selected taxonomies first in the list, that does not cause them to lose their hierarchy in any way. In your case, if you add the post to the "Jardim Cristal" category, the tree will be displayed as you expect.

Also, if you go to the taxonomies editing screen you'll see the hierarchy is also present there.

While a bit weird, indeed, this is just a visual feature for easier distinction of which taxonomies the post belongs to.