Same as in 18323
Debug a bit to be able to see the error.

Ex rule to be refactored: models/Question.php

/**
         * Question was new or title was updated : we add minor rules.
         * This rules don't broke DB, only potential “ExpressionScript Engine” issue.
         * usage of 'archiveimport' scenaruio for import LSA (survey archive) file
         **/
        if (empty($this->parent_qid)) {
            /* Unicity for ExpressionManager */
            $aRules[] = array('title', 'unique', 'caseSensitive' => true,
                'criteria' => array(
                    'condition' => 'sid=:sid AND parent_qid=0',
                    'params' => array(
                        ':sid' => $this->sid
                        )
                    ),
                'message' => gT('Question codes must be unique.'),
                'except' => 'archiveimport'
            );