C# SerialPort Crashing App After Close

protected ManualResetEvent threadStop = new ManualResetEvent(false);

//Init the scale thread
            if (scaleThread == null)
            {
                scaleThread = new Thread(new ThreadStart(InitScaleThread));
                scaleThread.IsBackground = true;
                scaleThread.Start();
            }

private void InitScaleThread()
{
    
    // --Code removed, just updating buttons and labels and pulling data into DataSet
    
    if (CommonMembers.IsValidDataSet(oDS))
    {
	DataRow oDR = oDS.Tables[0].Rows[0];

	using (scalePort = new SerialPort(oDR["Port"].ToString()))
	{
	    try
	    {
		scalePort.Parity = (System.IO.Ports.Parity)Enum.Parse(typeof(System.IO.Ports.Parity), oDR["Parity"].ToString());
		scalePort.BaudRate = Convert.ToInt32(oDR["BaudRate"].ToString());
		scalePort.StopBits = (System.IO.Ports.StopBits)Enum.Parse(typeof(System.IO.Ports.StopBits), oDR["StopBits"].ToString());
		scalePort.DataBits = Convert.ToInt32(oDR["DataBits"].ToString());
		scalePort.Handshake = Handshake.XOnXOff;
		scalePort.ReadTimeout = 2000;

		scalePort.Open();

		string data, prevdata;
		prevdata = "";
		while (scalePort.IsOpen)
		{
		    data = scalePort.ReadLine();

		    if ((data.Length > 0) && prevdata != data)
		    {
			prevdata = data;
			scalePort_DataReceived(scalePort, data);
		    }

		    Thread.Sleep(10);

		    if (threadStop.WaitOne(0))
		    {
		    	// Added the below as a test, although it shouldn't hurt anything
			scalePort.DtrEnable = false;
			scalePort.RtsEnable = false;
			scalePort.Close();
			break;
		    }
		}
	    }
	    catch (TimeoutException)
	    {
		// Do Nothing
	    }
	    catch (InvalidOperationException)
	    {
	    	// Added to try and capture error if any for testing only
	    	CommonMembers.SendSupportEmail();		
	    }
	    catch (UnauthorizedAccessException)
	    {
	    	// Added to try and capture error if any for testing only
	    	CommonMembers.SendSupportEmail();
	    }
	    catch (IOException)
	    {
	    	// Added to try and capture error if any for testing only
		CommonMembers.SendSupportEmail();
	    }
	}     
    }
    else
    {
	// -- Removed Code updating buttons and label, etc...
    }

}

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void scalePort_DataReceived(object sender, String DataRead)
{
    try
    {
	string value = "";
	float scaleValue = 0;

	char[] cData = DataRead.ToCharArray();

	// Break the data apart and find the numbers - Should probably be done with Regex
	for (int i = 0; i < cData.Length; i++)
	{
	    if (CommonMembers.IsNumeric(Convert.ToString(cData[i])))
		value += Convert.ToString(cData[i]);
	    else if (Convert.ToString(cData[i]) == "L" || Convert.ToString(cData[i]) == "T")
		break;
	    Thread.Sleep(1);
	}

	if (CommonMembers.IsFloat(value))
	{
	    scaleValue = float.Parse(value);
		
	    // Update PIN Location and gauge max values
	    if (scaleValue < 500)
		SetScaleMaxValue(500);
	    else if (scaleValue > arcScale.MaxValue)
		SetScaleMaxValue(scaleValue + 50);
	    else if (scaleValue < 0)
		SetScaleValue(0);
	    else
	    {
		SetScaleValue(scaleValue);
		SetScaleVisibleValue(scaleValue.ToString());
	    }
	}
    }
    catch { }
}

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// In Form_Closing Event
stopThread.Set();

if (scaleThread != null)
                {
// Added for testing
                    scaleThread.Abort();
                    // Added for testing
                    while (scaleThread.ThreadState != ThreadState.Stopped)
                    {
                        Thread.Sleep(500);
                    }
                }
                scaleThread = null;

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