Mutlipe Custom fileds order by , i reload the page , result different every time

I’m writing a query_post() like this.

$args = array(
    'post_type' =  DEBBING_TYPE_SLUG,
    'post_status'   =  'publish',
    'meta_query'    = array(
        array(
            'relation' = 'AND',
            'status_clause' = array(
                'key'       = '_debbing_status',
                // 'type'      = 'NUMERIC',
            ),
            'order_clause' = array(
                'key'       = '_debbing_order',
                // 'type'      = 'NUMERIC',
            ),
        )
    ),
    'orderby' = array(
        'status_clause'       = 'DESC',
        'order_clause'     = 'DESC',
    )
);

And use query monitor the sql is below :

SELECT SQL_CALC_FOUND_ROWS wp_posts.ID
FROM wp_posts
INNER JOIN wp_postmeta
ON ( wp_posts.ID = wp_postmeta.post_id )
INNER JOIN wp_postmeta AS mt1
ON ( wp_posts.ID = mt1.post_id )
WHERE 1=1
AND ( ( wp_postmeta.meta_key = ‘_debbing_status’
AND mt1.meta_key = ‘_debbing_order’ ) )
AND wp_posts.post_type = ‘debbing’
AND (wp_posts.post_status = ‘publish’
OR wp_posts.post_status = ‘private’)
GROUP BY wp_posts.ID
ORDER BY CAST(wp_postmeta.meta_value AS SIGNED) DESC, CAST(mt1.meta_value AS SIGNED) DESC
LIMIT 0, 10

Problem 1: Every time I reload the page, the result order is different.

Problem 2: Look like the result is less. I set the _debbing_status = 0 , for 3 posts. But the program only display 2 records. If I change the _debbing_status = 0 , for 4 posts , only didsplay 3 records.

Anyone know how to solve the problem ?

Demo URL: http://103.149.92.104/