Unfortunately that was too early. Now I only get 13 entries to root in sitemap.xml and the following errors in php-error.log
PHP Warning: count(): Parameter must be an array or an object that implements Countable in /pages/page-chlog.inc.php on line 166
PHP Warning: count(): Parameter must be an array or an object that implements Countable in /pages/page-chlog.inc.php on line 167