[TYPO3-mvc] Object not always found in repository

[ktt]

            Hello,            
           


            I'm using Extbase 1.3.2. And noticed, that although the object exists, sometimes repository function doesn't return it.
            Behaviour seems to be random.
            
            Functionality in controller:
            
            $myUsermodel = $this->userRepository->getUserByUsername((string)$username,1);
            
            if ( ($myUsermodel instanceof Tx_Myextension_Domain_Model_Dummyuser) && ($username === $myUsermodel->getUsername()) ){
        
                        $myUsermodel->setStarttime($userStartTime);
                        $myUsermodel->setEndtime($userEndTime);
                        $this->userRepository->update($myUsermodel);

            } else {
                    ...create new...
                    
                    
            Functionality in repository:
                    
                /*
                 *
                 * @param string $username The username
                 * @param int
                 * @return object
                 */
                 public function getUserByUsername($username, $limit){
                        if ($this->identityMap->hasIdentifier($username, $this->objectType)) {
                                $object = $this->identityMap->getObjectByIdentifier($username, $this->objectType);
                        } else {
                        
                                $query = $this->createQuery();
                                $query->setLimit((integer)$limit);

                                $query->matching(
                                                    $query->logicalAnd(
                                                        $query->equals('username', (string)$username),
                                                        $query->equals('tx_extbase_type', 'Tx_Myextension_Domain_Model_Dummyuser')
                                                    )
                                                );

                                $query->setOrderings(array('uid' => Tx_Extbase_Persistence_QueryInterface::ORDER_DESCENDING));
                                $result = $query->execute();
                            
                                $object = NULL;
                                
                                    if (count($result) > 0) {

                                                $object = $result->getFirst();
                                                $this->identityMap->registerObject($object, $username);

                                    }
                                
                        }
                        return $object;
                    
                }
                
                Thank you in advance,
                Kast