I am getting wrong data coming from LIS analyzer abacus diatron 380

public void SettingRS232()
       {
           try
           {
               serialPort1.PortName = comportName.Text;
               serialPort1.BaudRate = Convert.ToInt32(combaudrate.Text);
               serialPort1.DataBits = Convert.ToInt32(comdatabits.Text);
               serialPort1.StopBits = (StopBits)Enum.Parse(typeof(StopBits), comstopBits.Text);
               serialPort1.Parity = (Parity)Enum.Parse(typeof(Parity), comparityBits.Text);
               serialPort1.Handshake = (Handshake)Enum.Parse(typeof(Handshake), comparityBits.Text);
               serialPort1.ReadTimeout = 2000;
               serialPort1.WriteTimeout = 500;

               serialPort1.DtrEnable = true;
               serialPort1.RtsEnable = true;

               serialPort1.Open();

               serialPort1.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler);
               lblstatus.Text = "Port is now ready...";

           }
           catch (Exception ex)
           {
               lblstatus.Text = ex.Message;
           }
       }
       public void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
       {
           SerialPort sp = (SerialPort)sender;
           string indata = sp.ReadExisting();

           this.Invoke(new Action(delegate() { richTextBox1.Text = indata; }));
       } private void btnStart_Click(object sender, EventArgs e)
       {
           if (serialPort1.IsOpen)
           {
           }
           else
           {
               btnStart.BackColor = Color.Green;
               SettingRS232();
               btnStop.BackColor = default(Color);
           }

       }