Problem with Pagination

[eluser]Noisy[/eluser]
Ok here it comes:

The URL looks like: http://**.**/forum/news-und-ankuendigungen/1/test/&page=4
But it should look like this: http://**.**/forum/news-und-ankuendigungen/1/test/4

I have no idea why.
This is my config for the pagination

Code:

$page_config['base_url'] = base_url().'forum/'.$forenInfoArray['seo_titel'].'/'.$threadInfoArray['id'].'/'.seo(utf8_decode($threadInfoArray['titel'])).'/';
$page_config['total_rows'] = $post_anzahl;
$page_config['per_page'] = 2;
$page_config['uri_segment'] = 6;
$page_config['page_query_string'] = false;
//$page_config['query_string_segment'] = 'seite';

$this->pagination->initialize($page_config);
$page_numbers = $this->pagination->create_links();
            
[...]

$postsQuery = $this->db->get_where('forum_posts', $postsWhere, $limit, $offset);

What is wrong. Even if I set page_query_string on true nothing happens.
I'm so desperate. I have another pagination on my site and it's working fine.

Thanks in advance!