Rewrite/Change custom taxonomy slug

Try using the below code to overwrite arguments of already registered taxonomies.

function wp_modify_taxonomy() {

    // get the arguments of the already-registered taxonomy
    $custom_category_args = get_taxonomy( 'genre' );

    // make changes to the args
    $custom_category_args->rewrite['slug'] = 'chambers';
    $custom_category_args->rewrite['with_front'] = false;

    // re-register the taxonomy
    register_taxonomy( 'genre', 'chambers', (array) $custom_category_args );
}
add_action( 'init', 'wp_modify_taxonomy', 11 );