NEXTGEN & Other Custom Shortcode in the Same Page

Hello,
I have some problems about NEXTGEN Gallery and one other simple shortcode in the same page. The results are here:
– http://strigo.de/beta/galerie/

(there is only a thumbnail preview instead the gallery)

This problem is only when I use [insert_page page=”shortlink”].

My shortcode declared:

function pa_insertPage($atts, $content = null) {
 // Default output if no pageid given
 $output = NULL;

 // extract atts and assign to array
 extract(shortcode_atts(array(
 "page" => '' // default value could be placed here
 ), $atts));

 // if a page id is specified, then run query
 if (!empty($page)) {
 $pageContent = new WP_query();
 $pageContent->query(array('pagename' => $page));
 while ($pageContent->have_posts()) : $pageContent->the_post();
 // assign the content to $output
 $output = get_the_content();
 $output = apply_filters( 'the_content', get_the_content() );
 endwhile;
 }

 return $output;
}
add_shortcode('insert_page', 'pa_insertPage');

Thanks in advice!

(And btw, the “define( ‘NGG_DISABLE_FILTER_THE_CONTENT’, true );” doesn’t work)
https://wordpress.org/plugins/nextgen-gallery/