Error occurred when trying to assign language resource to task

Zend_Db_Statement_Exception: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '6-\{9e5db691-8dfd-44ec-8109-047e070e8343}' for key 'LEK_languageresources_taskassoc.tmmtId', query was: INSERT INTO `LEK_languageresources_taskassoc` (`languageResourceId`, `taskGuid`, `segmentsUpdateable`) VALUES (?, ?, ?)

core
File: /webs/instance-1021/vendor/shardj/zf1-future/library/Zend/Db/Statement/Pdo.php (235)Request: [https://translate5m.transline.de|https://translate5m.transline.de/] POST [https://translate5m.transline.de/editor/languageresourcetaskassoc]Trace:    #0 /webs/instance-1021/vendor/shardj/zf1-future/library/Zend/Db/Statement.php(303): Zend_Db_Statement_Pdo->_execute()
    #1 /webs/instance-1021/vendor/shardj/zf1-future/library/Zend/Db/Adapter/Abstract.php(480): Zend_Db_Statement->execute()
...
    #8 /webs/instance-1021/library/ZfExtended/Controllers/AAARestController.php(505): ZfExtended_Models_Entity_Abstract->save()
    #9 /webs/instance-1021/application/modules/editor/Controllers/LanguageresourcetaskassocController.php(81): ZfExtended_RestController->postAction()
    #10 /webs/instance-1021/vendor/shardj/zf1-future/library/Zend/Controller/Action.php(516): editor_LanguageresourcetaskassocController->postAction()
  ...
}