Why does a DataGridView row disappear when I first make empty in a particular column

Dear Sir

Why does a DataGridView row disappear when I first make empty in a particular column .

If I change the update in the "QTY" column to the value of 1 then I change it to the value of 0 after I empty it then the datagridview row is not lost but at the first time the form loads then I remove or make it blank in the qty column then the datagridview row becomes missing

Please guide me

Thanks

Result code in video

Imports System.ComponentModel
Imports System.Globalization
Imports System.Reflection

Public Class Form1
    Private BindingSource1 As BindingSource = Nothing
    Public Sub New()
        ' This call is required by the designer.
        InitializeComponent()
        ' Add any initialization after the InitializeComponent() call.
        ' To reduce the flickering...
        DataGridView1.GetType().
    GetProperty("DoubleBuffered",
                BindingFlags.Instance Or BindingFlags.NonPublic).
    SetValue(DataGridView1, True)

    End Sub
    Private Sub CalculateTotal()
        Dim tot As Double = 0
        For Each item As DataGridViewRow In DataGridView1.Rows
            Dim quantity As Double = 0
            Dim price As Double = 0
            If Not IsDBNull(item.Cells("Qty").Value) Then
                Double.TryParse(CType(item.Cells("Qty").Value, String), quantity)
            End If
            If Not IsDBNull(item.Cells("PRICE").Value) Then
                Double.TryParse(CType(item.Cells("PRICE").Value, String), price)
            End If

            tot += (quantity * price)
        Next item
        lblTotal.Text = tot.ToString("N")
End Sub
    Protected Sub updateDataSource()
        BindingSource1 = New BindingSource With {.DataSource = New BindingList(Of Products)}
        DataGridView1.DataSource = BindingSource1
        DataGridView1.AutoGenerateColumns = False
        DataGridView1.AllowUserToAddRows = False
        DataGridView1.Columns("PRICE").DefaultCellStyle.Format = "c2"
        DataGridView1.Columns("PRICE").DefaultCellStyle.FormatProvider = CultureInfo.GetCultureInfo("en-US")
 DataGridView1.Columns("TOTAL").DefaultCellStyle.Format = "c2"
        DataGridView1.Columns("TOTAL").DefaultCellStyle.FormatProvider = CultureInfo.GetCultureInfo("en-US")
BindingSource1.AddNew()
    End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        updateDataSource()
    End Sub
    Private Sub DataGridView1_CellEndEdit(
    sender As Object,
    e As DataGridViewCellEventArgs) Handles DataGridView1.CellEndEdit
        Dim dgv = DirectCast(sender, DataGridView)
        Dim PRICE As Double = Nothing, QTY As Double = Nothing, TOTAL As Double = Nothing
        If DataGridView1.Rows(e.RowIndex).Cells("QTY").Value IsNot Nothing Then
            If Not Double.TryParse(DataGridView1.Rows(e.RowIndex).Cells("QTY").Value.ToString(), QTY) Then
                QTY = 0
            End If
        Else
            QTY = 0
        End If
        DataGridView1.Rows(e.RowIndex).Cells("QTY").Value = QTY
        If DataGridView1.Rows(e.RowIndex).Cells("PRICE").Value IsNot Nothing Then
            If Not Double.TryParse(DataGridView1.Rows(e.RowIndex).Cells("PRICE").Value.ToString(), PRICE) Then
                PRICE = 0
            End If
        Else
            PRICE = 0
        End If
        DataGridView1.Rows(e.RowIndex).Cells("PRICE").Value = PRICE
        TOTAL = (QTY * PRICE)
        DataGridView1.Rows(e.RowIndex).Cells("TOTAL").Value = TOTAL
End Sub
  Private Sub DataGridView1_DataError(sender As Object, e As DataGridViewDataErrorEventArgs) Handles DataGridView1.DataError
        If e.Context = DataGridViewDataErrorContexts.Commit Then
            MessageBox.Show(String.Format("value is required.", e.ColumnIndex))
        End If
    End Sub
End Class
Public Class Products
    Public Property PRODUCTNAME() As String
    Public Property QTY() As Double
    Public Property PRICE() As Double
    Public Property TOTAL() As Double
End Class