Pre_Get_Posts order DESC not registering

Question

I've created a filter function to filter a post type items by it's meta value _item_price. The problem is that it only works in Ascending Order and I'm not sure why. My pre_get_posts function looks like this:

function frontend_items_filter( $query ) {
    global $page_items_id

    if(!is_page($page_items_id))
        return;

    if($query->query_vars['post_type'] == 'items' && isset($_GET['filter'])){
        $sort = $_GET['item_sort'];

        // Set Ordering Parameter
        if(isset($_GET['item_sort']) && !empty($_GET['item_sort'])){
            switch($_GET['item_sort']){

                case 'price_lowest':
                    $query->set('meta_key', '_item_price');
                    $query->set('orderby', 'meta_value_num title');
                    $query->set('order', 'ASC');
                        break;

                case 'price_highest':
                    $query->set('meta_key', '_item_price');
                    $query->set('orderby', 'meta_value_num title');
                    $query->set('order', 'DESC');
                         break;

                default:
                    $query->set('orderby', 'post_date title');
                    $query->set('order', 'ASC');
            }
        }
    }
    return $query;
}
add_action( 'pre_get_posts', 'frontend_items_filter' );

Before I save my price meta I'm verifying it's is_numeric(). I tried to print out my query and run the SQL directly into PHPmyadmin, If I take the SQL below and change ASC to DESC, in my PHPmyadmin the results don't change which is peculiar.

SELECT SQL_CALC_FOUND_ROWS  wp_posts.ID FROM wp_posts
    INNER JOIN wp_term_relationships 
        ON (wp_posts.ID = wp_term_relationships.object_id) 
    INNER JOIN wp_postmeta 
        ON (wp_posts.ID = wp_postmeta.post_id) 
    WHERE 1=1  
    AND ( wp_term_relationships.term_taxonomy_id IN (10) ) 
    AND wp_posts.post_type = 'items' 
    AND (wp_posts.post_status = 'publish' 
    OR wp_posts.post_status = 'private') 
    AND (wp_postmeta.meta_key = '_item_price' ) 
    GROUP BY wp_posts.ID 
    ORDER BY wp_postmeta.meta_value+0,wp_posts.post_title ASC LIMIT 0, 10

Every time it pulls my results back in _item_price Ascending order (lowest price to highest price). What could the problem possibly be? What else can I check / verify?

Edit I've tried this with a few other fields I have and it's the same result - it will show ASC but not DESC.

Answer 1

I'm not sure why, but it had to do with the title in my ordering, once I removed that everything started working fine. I'll leave this open for anyone who knows why.

$query->set('orderby', 'meta_value_num title'); - Does not Work

$query->set('orderby', 'meta_value_num'); - Works!