Program drops com port while receiving data from arduino VB.net - vb.net

Question

When running the code the program will run to complete one cycle, then the arduino must be disconnected and reconnected (unplugged and replugged in) in order to run again. Sometimes the program will even stop halfway through.
I am very new to VB programming and any help would be appreciated
There is no problem with the arduino code, it was fully tested before creating the VB user form.
tried running on multiple computers/Operating systems same results
Private Sub SerialPort1_DataReceived(sender As Object, e As SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
''reads data from arduino
Dim datastream As String
datastream = (SerialPort1.ReadLine)
'' RichTextBox1.Text = datastream
Data_manipulate(arr:=datastream)
End Sub
Public Sub Data_manipulate(ByRef arr As String)
''processes data to calculate linearity
Dim linearity As Single
Dim percent As Single
Dim nominal As Single
ReDim Preserve points(i)
ReDim Preserve counts(i)
Dim values As String() = arr.Split(New Char() {","c})
percent = values(0) / values(3)
nominal = values(1) / values(2)
linearity = (percent - nominal) * 100
TextBox3.Text = values(2) * (0.00118)
points(i) = linearity
counts(i) = nominal * 100
TextBox8.Text = (points).max
TextBox10.Text = points.Min
Chart1.Series("Linearity").Points.AddXY(counts(i), points(i))
''Chart1.Series("Linearity").Points.AddXY(counts(i), points(i))
If points.Max > NumericUpDown1.Value Then
TextBox8.BackColor = Color.Red
End If
If points.Min < -NumericUpDown1.Value Then
TextBox10.BackColor = Color.Red
End If
If nominal < 0.5 Then
TextBox13.Text = values(1) * (0.00118)
Dim Halfpercent As Double = values(1) * 0.00118
If ((0.5 * (values(2) * 0.00118)) - 0.015) < Halfpercent AndAlso Halfpercent < ((0.5 * (values(2) * 0.00118)) + 0.015) Then
TextBox13.BackColor = Color.LimeGreen
Else TextBox13.BackColor = Color.Red
End If
End If
If percent = 1 Then
Auto_Slope_And_Level_Button_Click()
End If
i += 1
End Sub
Private Sub Connect_Button_click(sender As Object, e As EventArgs) Handles Connect_Button.Click
If ComboBox1.SelectedItem Is Nothing Then
MessageBox.Show("Please Select a Port")
Return
End If
SerialPort1.BaudRate = 9600
SerialPort1.PortName = ComboBox1.SelectedItem
If Connect_Button.Text = "Connect" Then
Try
SerialPort1.Open()
Connect_Button.Text = "Connected"
Disconnect_Button.Text = "Disconnect"
Connect_Button.BackColor = Color.LimeGreen
Catch ex As Exception
End Try
Else
End If
End Sub
Private Sub Start_Button_Click(sender As Object, e As EventArgs) Handles Start_Button.Click
If SerialPort1.IsOpen Then
Chart1.Series("Linearity").Points.Clear()
ReDim points(0)
ReDim counts(0)
SerialPort1.Write(1)
TextBox8.Text = 0
TextBox10.Text = 0
TextBox2.Text = 0
Else
MessageBox.Show("Not Connected")
Return
End If
End Sub
Private Sub Disconnect_Button_Click(sender As Object, e As EventArgs) Handles Disconnect_Button.Click
Try
SerialPort1.Close()
Disconnect_Button.Text = "Disconnected"
Connect_Button.Text = "Connect"
Connect_Button.BackColor = Color.FromArgb(255, 0, 0)
Catch ex As Exception
End Try
End Sub
Private Sub ComboBox1_DropDown(sender As Object, e As EventArgs) Handles ComboBox1.DropDown
ComboBox1.Items.Clear()
Try
For Each port As String In SerialPort.GetPortNames
ComboBox1.Items.Add(port)
Next
ComboBox1.SelectedItem = ""
Catch ex As Exception
End Try
End Sub
A "com port does not exist" error will occur if you don't reset between runs.
If the program stops partway through the computer needs either a log-off or restart to reconnect with the arduino.