Your filter has a bug in it, namely when you call is_main_query, you're not checking if the passed query is the main query, your checking if the currently active query is the main query, which will always be true.

So instead try this:

    add_action( 'pre_get_posts', 'some_name');
    function some_name($query) {
        if ($query->is_front_page() && $query->is_main_query()) {
            $query->set( 'post_type', 'some_post_type' );
            return;
        }
    }