I'm trying to fix the broken page problem, I found that there are some issues with the permalink of these broken pages. The slug of these pages has the same numbers as the one in the middle of the link below:

/

Code in functions.php:

$args = array( 
        'labels' => $labels,
        'hierarchical' => true,
        
        'supports' => array( 'title', 'editor', 'excerpt', 'tag', 'thumbnail'),
        'public' => true,
        'show_ui' => true,
        'show_in_menu' => true,
        
        
        'show_in_nav_menus' => true,
        'publicly_queryable' => true,
        'exclude_from_search' => false,
        'has_archive' => false,
        'query_var' => true,
        'can_export' => true,
        'taxonomies' => array( 'post_tag' ),
        
        'rewrite' => array('slug'=>'product','with_front'=>false),
        'capability_type' => 'post'
    );