Custom post type permalink broken : 3 match for a single custom post.

Hi All,
I submit you a problem that drives me mad… I created a custom post type called “product” with custom permalinks using this very good tutorial : https://shibashake.com/wordpress-theme/custom-post-type-permalinks-part-2. Everything was working well since… I flushed all the rewrite rules ! #BigFail

Here is my code, and I will comment what I’ve done. I hope you will find what is wrong.

1) Registering of custom post type called “product”:

add_action('init', 'my_products_init');
function my_products_init() {
        $args = array(
                'label' => __('My Product DB'),
                'singular_label' => __('My Product DB'),
                'public' => true,
                'show_ui' => true,
                '_builtin' => false,
                '_edit_link' => 'post.php?post=%d',
                'capability_type' => 'post',
                'hierarchical' => false,
                'publicly_queryable' => true,
                'query_var' => true,
                'rewrite' => false,
                'supports' => array('title', 'editor', 'thumbnail', 'comments')
        );
        register_post_type( 'product' , $args );
}

I created a lot of custom posts “products” so no problem at this stage.

2/ I registered a custom permalink structure for “product” post types, which is composed of 2 %tags% :

add_action('init', 'my_rewrite_init');
function my_rewrite_init()
{
        global $wp_rewrite;
        $wp_rewrite->add_rewrite_tag("%product%", '([^/]+)', "product=");
        $wp_rewrite->add_rewrite_tag("%producttitle%", '([^/]+)', 'producttitle=');

        $products_structure = '/Product-DB/%producttitle%/%product%/The-Product';
        $wp_rewrite->add_permastruct('product', $products_structure, false);
}

At this stage, the link of each post is well replaced my the permalink structure “products_structure”. So no problem at this stage too.

3/ Substitution rules of %producttitle% tag with “_producttitle” custom field.

add_filter('post_type_link', 'producttitle_permalink', 10, 3);
function producttitle_permalink($permalink, $post, $leavename)
{
        $no_data = 'no-title';
        $post_id = $post->ID;
        if($post->post_type != 'product' || empty($permalink) || in_array($post->post_status, array('draft', 'pending', 'auto-draft')))
                return $permalink;
        $var1 = get_post_meta($post_id, '_producttitle', true);
        $var1 = sanitize_title($var1);
        if(!$var1) { $var1 = $no_data; }
                $permalink = str_replace('%producttitle%', $var1, $permalink);
        return $permalink;
}

Again, each %tag% is replaced.

A sample target link of my custom products post is https://www.mysite.com/my-wpmu-blogid/Product-DB/product-title-sample/s79925215/The-Product/ BUT when I load this link I got a 404 error. I don’t understand why because, again, EVERYTHING was working well since 1 week, till I decided to “flush rewrite rules”.

I installed Rewrite Rules Inspector and this plugin says 3 rules match my custom products URLs :

Product-DB/[^/]+/[^/]+/([^/]+)/?$	index.php?attachment=$matches[1]	missing
Product-DB/([^/]+)/([^/]+)/The-Product(/[0-9]+)?/?$	index.php?producttitle=$matches[1]&product=$matches[2]&page=$matches[3]	missing
(.?.+?)(/[0-9]+)?/?$	index.php?pagename=$matches[1]&page=$matches[2]	page

I don’t know why the “page” post type is matched… perhaps this is the source of my problem. And if so, I don’t understand why it doesn’t work anymore as it worked yesterday.

Any idea ?

Best regards,
–Looic