Custom Post Types using wrong template (index) instead of archive-{type}.php - previously worked as expected

Question

I have several custom post types on a site where top-level nav items use archive-{post-type}.php templates of the post types. These have recently had a template problem and they now use the index.php template, instead of their archive template. This is possibly after I added a custom taxonomy to the end of functions.php (below), but only because this is the most recent significant change to functions. They still use the correct archive templates on our production site, but not on the development site, where changes have been made.

I've tried removing the taxonomy action, no change.

I've tried saving permalinks in admin settings, no change.

Also maybe relevant: this also only affects top-level templates - there are several custom post types with rewrites to eg domain.com/media-center/articles - and the articles for these work as expected.

I've not faced this issue before and haven't yet found any solutions that resolve it. Is there anything that I can check that might be causing it - or a way to get to the bottom of the issue?

The recently added taxonomy:

add_action( 'init', 'create_year_taxonomy' );
function create_year_taxonomy() {
  
  // translations for GUI
  $labels = array(
    'name' => _x( 'Edition Year', 'taxonomy general name' ),
    'singular_name' => _x( 'Year', 'taxonomy singular name' ),
    'search_items' =>  __( 'Search Years' ),
    'all_items' => __( 'All Years' ),
    'parent_item' => __( 'Parent Year' ),
    'edit_item' => __( 'Edit Year' ), 
    'update_item' => __( 'Update Year' ),
    'add_new_item' => __( 'Add New Year' ),
    'new_item_name' => __( 'New Year' ),
    'menu_name' => __( 'Years' ),
  );    
  
  // register the taxonomy
  register_taxonomy('year',array('the_street_view'), array(
    'hierarchical' => true,
    'labels' => $labels,
    'show_ui' => true,
    'show_in_rest' => true,
    'show_admin_column' => true,
    'query_var' => true,
    'rewrite' => array( 'slug' => 'year' ),
  ));
}

Answer 1

The issue was, in fact, the new taxonomy using "year" clashes with the query.

Wordpress was accepting year=about-us in the query chain for instance, as year was a taxonomy, before the expected page=about-us - preventing it from appearing as a page and using the index.php template as there is no "year" template.

I changed year to a more custom slug edition-year in functions.php and flushed the permalinks, which resolved the issue.