Contentmanager: "Unsecure page token!"

Beim Versuch den Contentmanager von uralten Einträgen zu befreien, kommt o.g. Meldung.
Betrifft GX3.0.0 und GX3.1.1 b2
Im Logfile:

Code:

2016-06-17 12:17:53 (347947091a529a54941baba216b4dd46) SECURITY ERROR(256): "Unsecure page token 5ac43724b3b81791b4a24ed3817c1139" in /www/htdocs/XXXXXX/_gx25/system/classes/security/PageToken.inc.php:59

#2    File: /www/htdocs/XXXXXX/_gx25/system/classes/security/PageToken.inc.php:59

    Code:
│    line 57:         $t_additional_info .= 'Generated token array:' . "\r\n" . print_r($this->v_page_token_array, true);
│    line 58:        
├─    line 59:         $coo_logger->error($t_message, 'security', 'security', 'error', 'SECURITY ERROR', E_USER_ERROR, $t_additional_info);
│    line 60:         $coo_logger->write_stack(array('security'));
│    line 61:        

#1    File: /www/htdocs/XXXXXX/_gx25/system/classes/security/PageToken.inc.php:43

    Class: PageToken
        - $v_page_token_array: ### Cannot access protected property PageToken::$v_page_token_array ###
        - $v_max_array_size: ### Cannot access protected property PageToken::$v_max_array_size ###

Mögliche Ursache & Abhilfe?