Hi!
It might be possible via using a small custom code snippet. Try add this custom code to the functions.php in your theme/child theme directory. Before editing, please make sure to have a full site back-up just in case!
add_filter( 'asp_results', 'asp_get_main_prod_img', 10, 1 );
function asp_get_main_prod_img($results) {
foreach ( $results as $k => &$r ) {
if ( isset($r->post_type) && $r->post_type == 'product_variation' ) {
$wc_prod_var_o = wc_get_product( $r->id );
$img = wp_get_attachment_image_src(
get_post_thumbnail_id($wc_prod_var_o->get_parent_id()),
'single-post-thumbnail'
);
if (isset($img, $img[0]) && !is_wp_error($img))
$r->image = $img[0];
}
}
return $results;
}
This should hopefully resolve the issue.