version : 3.1.7 (Build - 2017042800) (2016071102)
locallib.php : function questionnaire_delete_responses($qid)
parameter is $qid, but in deletion processing of 'questionnaire_response' and 'questionnaire_attempts' it is coded as if it is $rid.
In this case, irrelevant responses are deleted.
function questionnaire_delete_responses($qid) {
:
$status = $status && $DB->delete_records('questionnaire_response', array('id' => $qid)); //Problem
$status = $status && $DB->delete_records('questionnaire_attempts', array('rid' => $qid)); //Problem
return $status;
}