When scanning logs Zabbix agent tries to add the matched lines to the output buffer. If output buffer is full it will be flushed beforehand. However if the flushing fails (server is offline, network down etc), then agent immediately will try to repeat this again and again until the maxlines per second limit has reached.
There is little sense in trying to force the value into buffer, as it's little likely that it will succeed after first fail. So we could return after the first failure. And as it is not an error success result would have to be returned.