Secondary menu dropdown fails

Hi,
Thanks for your support.
I have create a top-bar div in child theme with wp_body_open hook and insert in it in functions.php:

echo "<div class='gp-top-header grid-container' style='background-color:brown'>";
    wp_nav_menu( array(
        'theme_location' => 'top-menu',
        'container_class' => 'top-menu-class' ) );
    echo "</div>";

This insert a secondary menu in this top-bar, but the dropdown submenu doesnt show fine, it appears as you can see in the image: https://ibb.co/mXdnkSF
"Iniciar sesión" has a submenu which contains Contacto and Registrarse links and stands fixed in screen, dont do the dropdown.

What I have to do to make the submenu dropdown works?

Thanks in advanced