get_posts() and Taxonomy

Have you tried it with the operator ‘AND’.
https://codex.www.ads-software.com/Function_Reference/WP_Query#Taxonomy_Parameters

$args = array(
    'post_type' => 'advert',
    'tax_query' => array(
        array(
            'taxonomy' => 'type',
            'field' => 'slug',
            'terms' => array( 'persistent', 'conventional' ),
            'operator' => 'AND'
        )
    )
);
get_posts( $args );

or with the ‘relation’ parameter ‘AND’:

$args = array(
    'post_type' => 'advert',
    'tax_query' => array(
        'relation' => 'AND',
        array(
            'taxonomy' => 'type',
            'field' => 'slug',
            'terms' => array( 'persistent' )
        ),
        array(
            'taxonomy' => 'type',
            'field' => 'slug',
            'terms' => array( 'conventional' )
        ),
    )
);
get_posts( $args );

https://codex.www.ads-software.com/Template_Tags/get_posts