Sorry, that was the wrong snippet.
Can you try this instead?:
add_action( 'after_setup_theme', 'tu_move_navigation' );
function tu_move_navigation() {
remove_action( 'generate_after_header', 'generate_add_navigation_after_header', 5 );
add_action( 'generate_after_header', 'generate_add_navigation_after_header', 99 );
}