Some times get this DB errors, is there anything that can be done about this?

[INSERT INTO ost_thread_referral SET thread_id = 15628, object_id = 4, object_type = 'D', created = NOW()]
Duplicate entry '4-D-15628' for key 'ref' 
---- Tracks back---- 
#0 (Root) source/include/mysqli.php(211): osTicket->logDBError() 
#1 (Root) source/include/class.orm.php(3482): db_query() 
#2 (Root) source/include/class.orm.php(658): MySqlExecutor->execute() #3 (Root) source/include/class.thread.php(1961): VerySimpleModel->save() #4 (Root) source/include/class.thread.php(380): ThreadReferral::create() #5 (Root) source/include/class.ticket.php(3039): Thread->refer() 
#6 (Root) source/include/class.thread.php(1418): Ticket->systemReferral() #7 (Root) source/include/api.tickets.php(187): ThreadEntry::lookupByEmailHeaders() #8 (Root) source/include/class.mailfetch.php(84): TicketApiController->processEmail() #9 (Root) source/include/class.mailfetch.php(137): osTicket\Mail\Fetcher->processMessage() #10 (Root) source/include/class.email.php(1129): osTicket\Mail\Fetcher->processEmails() #11 (Root) source/include/class.mailfetch.php(254): MailBoxAccount->fetchEmails() #12 (Root) source/include/class.cron.php(25): osTicket\Mail\Fetcher::run() #13 (Root) source/scp/autocron.php(61): Cron::MailFetcher() 
#14 {main}

[INSERT INTO ost_thread_referral SET thread_id = 15448, object_id = 4, object_type = 'D', created = NOW()] Duplicate entry '4-D-15448' for key 'ref' ---- Backtrace ---- #0 (root)/include/mysqli.php(211): osTicket->logDBError() #1 (root)/include/class.orm.php(3482): db_query() #2 (root)/include/class.orm.php(658): MySqlExecutor->execute() #3 (root)/include/class.thread.php(1961): VerySimpleModel->save() #4 (root)/include/class.thread.php(380): ThreadReferral::create() #5 (root)/include/class.ticket.php(3039): Thread->refer() #6 (root)/include/class.thread.php(1418): Ticket->systemReferral() #7 (root)/include/api.tickets.php(187): ThreadEntry::lookupByEmailHeaders() #8 (root)/include/class.mailfetch.php(84): TicketApiController->processEmail() #9 (root)/include/class.mailfetch.php(137): osTicket\Mail\Fetcher->processMessage() #10 (root)/include/class.email.php(1129): osTicket\Mail\Fetcher->processEmails() #11 (root)/include/class.mailfetch.php(254): MailBoxAccount->fetchEmails() #12 (root)/include/class.cron.php(25): osTicket\Mail\Fetcher::run() #13 (root)/include/class.cron.php(110): Cron::MailFetcher() #14 (root)/include/api.cron.php(15): Cron::run() #15 (root)/include/api.cron.php(45): CronApiController->run() #16 (root)/api/cron.php(23): LocalCronApiController::call() #17 {main}