[vb.net][Visual Studio] Refreshing Excel pivot retuns an error

Question

I use the code below to test the refresh speed of an excel sheet. The problem is, when I choose to refresh the pivot table, I get the error in the print screen attached. The weird thing is that I hit continue and it continues with no issue, and does what it's supposed to be (refreshes the pivot), and the error is not repeated untill the next first run.

Any ideas on how I can get rid of the error?

    Private Sub btlCalculate_Click(sender As Object, e As EventArgs) Handles btlCalculate.Click
        'https://codesnippets.fesslersoft.de/measure-execution-time-of-a-action/

        'Dim time0 = Now()
        Dim WB As Excel.Workbook = Globals.ThisAddIn.Application.ActiveWorkbook
        Dim WS As Excel.Worksheet = Globals.ThisAddIn.Application.ActiveSheet
        Dim AVG As Double, total As Double, I
        Dim PT As Excel.PivotTable

        Dim watch = Stopwatch.StartNew()

        On Error Resume Next

        If chkPivot.Checked Then
            For Each PT In WS.PivotTables
                PT.RefreshTable()
            Next
        Else
            WS.Calculate()
        End If


        watch.Stop()

        Dim intervalToMs = watch.Elapsed.TotalMilliseconds

        With Me.DataGridView1
            Dim rowI As String() = New String() { .RowCount, WS.Name, intervalToMs, TimeOfDay.ToString("HH:mm:ss")}
            .Rows.Add(rowI)

            For I = 0 To .Rows.Count - 2
                total += CDbl(.Rows(I).Cells(2).Value)
            Next

            AVG = total / (.Rows.Count - 1)
        End With

        txtAvg.Text = AVG

        On Error GoTo 0
    End Sub