Why query_vars get altered in WP_Query Object?

I am having problems when querying a WP_Query Object when a user has a role different than administrator

My WP_Query is this:

function remove_new_c_post($author_id,$value_id) {

        $query = new WP_Query( array(
            'post_type' => 'custom_post_type',
            'author' => $author_id,
            'meta_query' => array(
            'relation' => 'AND',
                array(
                    'key'     => 'value_id',
                    'value'   => $value_id,
                    'compare' => 'LIKE',
                ),
            ),
            'order' => 'ASC'

            ));

        if ( $query->have_posts() ) : while ( $query->have_posts() ) : $query->the_post();
            wp_delete_post( get_the_ID() );
        endwhile;
        wp_reset_postdata();
        endif;

}

For some reason when the query is run by a user other than the administrator, this is the result:

WP_Query Object
(
    [query] => Array
        (
            [post_type] => custom_post_type
             => 70
            [meta_query] => Array
                (
                    [relation] => AND
                    [0] => Array
                        (
                            [key] => value_id
                            [value] => 86
                            [compare] => LIKE
                        )

                )

            [order] => ASC
        )

    [query_vars] => Array
        (
            [post_type] => custom_post_type
             => 86 //<--- THIS SHOULD BE 70
            [meta_query] => Array
                (
                    [relation] => AND
                    [0] => Array
                        (
                            [key] => value_id
                            [value] => 86
                            [compare] => LIKE
                        )

                ) 
            [order] => ASC
...

Please notice the author in query_vars it is 86 when it should be 70. Why is this being altered?

EDIT:

I just tried to set the query_var $query->set( 'author', $author_id ); and it kept the author_id intact; howevever, the mysql keeps getting altered:

  [request] => SELECT SQL_CALC_FOUND_ROWS  dlwp_posts.ID
               FROM dlwp_posts
               INNER JOIN dlwp_postmeta ON ( dlwp_posts.ID = dlwp_postmeta.post_id )   
               WHERE 1=1  AND dlwp_posts.post_author IN (86)
                 AND dlwp_posts.post_type="custom_post_type"
                 AND (dlwp_posts.post_status="publish"
                   OR dlwp_posts.post_status="future"
                   OR dlwp_posts.post_status="draft"
                   OR dlwp_posts.post_status="pending"
                   OR dlwp_posts.post_status="private")
                 AND (( dlwp_postmeta.meta_key = 'value_id'
                   AND CAST(dlwp_postmeta.meta_value AS CHAR) LIKE '%86%' )

Milo’s comment about pre_get_posts helped solve this issue for me. In my case the parent theme used the pre_get_posts action to explicitly set the post_type for all author pages. It wasn’t in the functions.php, but I was able to find it by searching the theme for instances of pre_get_posts. (I used grep -R "pre_get_posts" . -l from the command line to find the file.)

If you’re not using a child theme, you could potentially just delete the problematic function and its add_action().

If you are using a child theme, to maintain upgradability of the parent theme, you can use the remove_action function…

Problematic Action existing in Parent Theme:

function problematic_parent_action( &$query ) {
  if ($query->is_author) {
    $query->set( 'post_type', array( 'problematic_parent_post_type' ) );
  }
}
add_action( 'pre_get_posts', 'problematic_parent_action' );

Resolution added to Child Theme:

function remove_problematic_parent_action() {
  remove_action( 'pre_get_posts', 'problematic_parent_action' );
}
add_action( 'init', 'remove_problematic_parent_action');