#REF! after refresh workbook

Question

With some of my workbooks I get a #REF! error after updating my workbook. I have to filter data to a worksheet Januari to filter Januari, and get a total sum in Sheet Total.

The code I have is working perfectly, but when I want to copy the total from column "C" to another worksheet I get a #REF! error. Here is the line I get in my original sheet: =SOM('WABO Oktober'!#VERW!), where is should be: =SOM('WABO Oktober'!E:E) It does not happen in all the workbooks, just the one I need the most.

Here is a example of my code.

Sub Test()

    Dim My_Range As Range
    Dim Maand As String
    Maand = ActiveSheet.Name

    ' This is the name of the First part of the filtersheet
    Naam = ("filter") 

    ' Make sure sheet is visible
     Sheets((Naam) & " " & Maand).Visible = True
     Sheets(Maand).Select

    ' Range on active sheet
    Set My_Range = Range("A2:Y999")
        My_Range.Parent.Select

    'Remove AutoFilter
    My_Range.Parent.AutoFilterMode = False

    ' Select the columns you want to filter
    My_Range.AutoFilter Field:=2, Criteria1:="y"

    'Copy/paste the visible data to the new worksheet
    Sheets((Naam) & " " & Maand).Select
    My_Range.Parent.AutoFilter.Range.Copy
        With ActiveSheet.Range("A1")
            .PasteSpecial Paste:=8
            .PasteSpecial xlPasteValues
            .PasteSpecial xlPasteFormats
            Application.CutCopyMode = False
            .Select
    End With

    'AutoFit All Columns on Worksheet
    ActiveSheet.Cells.EntireColumn.AutoFit

    'Close AutoFilter
    My_Range.Parent.AutoFilterMode = False

    ' Remove colums to create data filter Januari
    Range("A:A").Select
    Range("C1").Activate
    Selection.Delete Shift:=xlToLeft

    ' Got to cell A1
    ActiveSheet.Range("A1").Select

    'Go back to the  "Maand" Sheet
    Worksheets(Maand).Activate
    ActiveSheet.Range("A1").Select

    'Hide the filter Januari sheet
    Sheets((Naam) & " " & Maand).Visible = False

    'Refresh workbook
    ActiveWorkbook.RefreshAll

End Sub