Parent Taxonomy Slug Repeats on Archive Pages

I was able to recreate the issue. It’s a combination of WP Better Permalinks and using taxonomies as menu items in the site navigation. Here are the steps I used to create the problem:

1. Install Custom Post Type UI (or create a custom post type and taxonomy):

• Go to CTP UI > Tools. On the Post Type tab, paste the following to import the Products Category (to ensure we have the same settings): {"products":{"name":"products","label":"Products","singular_label":"Product","description":"","public":"true","publicly_queryable":"true","show_ui":"true","show_in_nav_menus":"true","show_in_rest":"false","rest_base":"","rest_controller_class":"","has_archive":"true","has_archive_string":"products","exclude_from_search":"false","capability_type":"page","hierarchical":"true","rewrite":"true","rewrite_slug":"products","rewrite_withfront":"false","query_var":"true","query_var_slug":"","menu_position":"21","show_in_menu":"true","show_in_menu_string":"","menu_icon":"dashicons-cart","supports":["title","editor","thumbnail","page-attributes"],"taxonomies":["product_category"],"labels":{"menu_name":"Products","all_items":"All Products","add_new":"Add New","add_new_item":"Add New Product","edit_item":"Edit Product","new_item":"New Product","view_item":"View Product","view_items":"View Products","search_items":"Search Products","not_found":"No Products Found","not_found_in_trash":"No Products Found in Trash","parent":"Parent Product:","featured_image":"Featured Product Image","set_featured_image":"Set Featured Product Image","remove_featured_image":"Remove Featured Product Image","use_featured_image":"Use as Featured Product Image","archives":"Product Archives","insert_into_item":"Insert into Product","uploaded_to_this_item":"Uploaded to this Product","filter_items_list":"Filter Products","items_list_navigation":"Products List Navigation","items_list":"Products List","attributes":"Products Attributes","parent_item_colon":"Parent Product:","name_admin_bar":""},"custom_supports":""}}
• Click the Taxonomies tab at the top of the Tools panel. Paste the following to create the Product Category (to ensure we have the same settings): {"product_category":{"name":"product_category","label":"Product Categories","singular_label":"Product Category","description":"","public":"true","publicly_queryable":"true","hierarchical":"true","show_ui":"true","show_in_menu":"true","show_in_nav_menus":"true","query_var":"true","query_var_slug":"","rewrite":"true","rewrite_slug":"products","rewrite_withfront":"0","rewrite_hierarchical":"1","show_admin_column":"true","show_in_rest":"false","show_in_quick_edit":"true","rest_base":"","rest_controller_class":"","labels":{"menu_name":"","all_items":"","edit_item":"","view_item":"","update_item":"","add_new_item":"","new_item_name":"","parent_item":"","parent_item_colon":"","search_items":"","popular_items":"","separate_items_with_commas":"","add_or_remove_items":"","choose_from_most_used":"","not_found":"","no_terms":"","items_list_navigation":"","items_list":""},"meta_box_cb":"","object_types":["products"]}}

• Create 3 Product Categories:

1. Parent Category
2. Child Category – set the parent as Parent Category
3. Grandchild Category – set the parent as Child Category

• Create a Product page. Give it a Product Category of Grandchild Category.
• Install WP Better Permalinks
• Set the Products URL structure to include Product Category
• Create a Menu (Appearance > Menus) in the Primary menu location
• Add all three Product Categories (you may need to turn on their visibility by opening the Screen Options panel at the top of the Menus page). Nest Child Category under Parent Category and Grandchild Category under Child Category to create a dropdown.
• View the site and click on either Child Category or Grandchild Category from the dropdown. The URL structure will duplicate the parent/grandparent section of the URL.

Some additional notes/troubleshooting I’ve done:

• In the Settings > WP Better Permalinks, turning off the taxonomy in the URL does not affect the performance of the taxonomies, but does break the permalinks to the eventual single Product – a 404 page shows.
• Deleting the plugin outright resets the taxonomy URLs in the navigation, but the final single Product URL remains broken and results in a 404 page.
• Reinstalling WP Better Permalinks and adding the taxonomy back to the URL structure settings <b>does</b> fix the single Product URL, but the taxonomy URLs from the menu repeat once again.
• Setting the taxonomy URLs as custom URLs in the navigation does not help. There is a redirect created somewhere that forces the duplicate URL structure.
• Adding a 301 redirect results in an infinite loop and crashes the site.

Thanks for the help!

Yes, that solved it! Thank you for both taking the time, and for the explanation.