What causes Microsoft excel error "Removed Records: Named range from /xl/workbook.xml part (Workbook)"

I have a large Microsoft Excel file that is shared between users in my office. The file has a macro and a set of data validation. The file is used the last two weeks of every third month. The file worked perfectly before Christmas, however, we encountered errors in March.The following error appeared when the file was opened.

After clicking yes, the following appeared.

The code for the macro is:

 Sub Update()

 'Declaring Variables.
  Dim Number_Rows As Long
  Dim Oppt As String
  Dim Array_Oppt() As String
  Dim Rows_Array As Integer

 'Stops screen refreshing to save time.
  Application.ScreenUpdating = False

 'removing any data validation and conditional formatting
  Sheet1.Activate
  Cells.Select
  Selection.Validation.Delete
  Selection.FormatConditions.Delete


 'Assigning value to array.
  Rows_Array = 0
  ReDim Preserve Array_Oppt(Rows_Array)


 'Moving "Other" rows to the end of the data
  Sheet1.Select
  Selection.AutoFilter Field:=23, Criteria1:= _
  "OTHER"

  Range("A2", Cells(Rows.Count,       "A").End(xlUp)).SpecialCells(xlCellTypeVisible).Cells(1, 1).Select
 Selection.EntireRow.Select
 Range(Selection, Selection.End(xlDown)).SpecialCells(xlCellTypeVisible).Select
 Selection.Copy
 Sheet8.Select
 Sheet8.Range("A1").Select
 ActiveSheet.Paste
 Sheet1.Select
 Range("A2", Cells(Rows.Count, "A").End(xlUp)).SpecialCells(xlCellTypeVisible).Cells(1, 1).Select
 Selection.EntireRow.Select
 Range(Selection, Selection.End(xlDown)).SpecialCells(xlCellTypeVisible).Select
 Selection.Delete Shift:=xlUp
 Selection.AutoFilter

 Number_Rows = Application.WorksheetFunction.CountA(Range("A:A"))
 Sheet8.Select
 Selection.Cut
 Sheet1.Activate
 Range("A" & Number_Rows + 1).Select
 ActiveSheet.Paste

 'Counting number of rows.
  Number_Rows = Application.WorksheetFunction.CountA(Range("A:A"))

  'Loop to check if oppt if unit or non unit deal. Checks if oppt is in array and adds oppt if not.
 'Calculates total revenue per opp.
  For i = 2 To Number_Rows

  Oppt = Range("I" & i)

'In array already.
If UBound(Filter(Array_Oppt, Oppt)) >= 0 Then

    'Non Unit deal in the array already. Deletes line and shifts row up as well as i up.
    If Range("W" & i) = "OTHER" Then
    Rows(i).Select
    Selection.Delete Shift:=xlUp
    Number_Rows = Number_Rows - 1
    i = i - 1

    'Unit deal in the array already.
    Else
    Range("J" & i) = ""
    End If

'Not in array so needs to be added.
Else
Range("J" & i) = Application.WorksheetFunction.SumIf(Range("I:I"), Oppt, Range("J:J"))

    If Range("W" & i) = "OTHER" Then

    Range(Cells(i, 19), Cells(i, 26)) = ""

    Else
    End If

'Redefines the size of the array factoring in new added row.
ReDim Preserve Array_Oppt(Rows_Array)
Array_Oppt(Rows_Array) = Oppt
Rows_Array = Rows_Array + 1
End If

Next


'Adds blank column for business manager.
 Columns("H:H").Select
 Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
 Range("H1") = "Business Manager"


 'Updates the titles of the last columns in  file
  Range("AB1") = Date - 2
  Range("AC1") = Date - 1
  Range("AD1") = "Today"
  Range("AE1") = "Focus List"
  Range("AF1") = "% Chance"
  Range("AG1") = "Allocation Status"
  Range("AH1") = "New PO Date"
  Range("AI1") = Date - 3
  Range("AJ1") = Date - 4
  Range("AK1") = Date - 5
  Range("AL1") = Date - 6
  Range("AM1") = Date - 7
  Range("AN1") = Date - 8
  Range("AO1") = Date - 9
  Range("AP1") = Date - 10
  Range("AQ1") = "Partner Grouping"
  Range("AR1") = "VNX Models"
  Range("AS1") = "Commit + X"
  Range("AT1") = "Country"
  Range("AU1") = "Theater"


  'Moves to Sheet2 and copies Upside X column B to the end (column AV) for the purpose of VLookup. Then returns to Sheet1.
Sheet2.Activate
Sheet2.Columns("B:B").Select
Application.CutCopyMode = False
Selection.Copy
Sheet2.Columns("AV:AV").Select
ActiveSheet.Paste
Sheet1.Activate


'Loop to add Linked status; and to complete VLookups from yesterday.
 For i = 2 To Number_Rows

'If to check linked status
If Range("L" & i) = "" Then
Range("M" & i) = "Not Linked"

Else
Range("M" & i) = "Linked"
End If


'Vlookups
On Error Resume Next
Err.Clear
'Vlookup to add business manager
Sheet1.Range("H" & i) = Application.VLookup(Sheet1.Range("G" & i), Sheet3.Range("A:B"), 2, False)
'Vlookup to add comments from 2 days ago to column AB
Sheet1.Range("AB" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 20, False)
'Vlookup to add comments from yesterday to column AC
Sheet1.Range("AC" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 21, False)
'Vlookup to add data from Focus List column
Sheet1.Range("AE" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 22, False)
'Vlookup to add data from % Chance column
Sheet1.Range("AF" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 23, False)
'Vlookup to add data from Allocation Status column
Sheet1.Range("AG" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 24, False)
'Vlookup to add data from New PO Date column
Sheet1.Range("AH" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 25, False)
'Vlookup to add data from 3 days ago to column AI
Sheet1.Range("AI" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 19, False)
'Vlookup to add data from 4 days ago to column AJ
Sheet1.Range("AJ" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 26, False)
'Vlookup to add data from 5 days ago to column AK
Sheet1.Range("AK" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 27, False)
'Vlookup to add data from 6 days ago to column AL
Sheet1.Range("AL" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 28, False)
'Vlookup to add data from 7 days ago to column AM
Sheet1.Range("AM" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 29, False)
'Vlookup to add data from 8 days ago to column AN
Sheet1.Range("AN" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 30, False)
'Vlookup to add data from 9 days ago to column AO
Sheet1.Range("AO" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 31, False)
'Vlookup to add data from 10 days ago to column AP
Sheet1.Range("AP" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AR"), 32, False)
'Vlookup to add data to VNX Models column AR from VNX Models sheet 5 using Item Number column
Sheet1.Range("AR" & i) = Application.VLookup(Sheet1.Range("W" & i), Sheet5.Range("A:B"), 2, False)
'Vlookup to add data to Upside X column B
Sheet1.Range("B" & i) = Application.VLookup(Sheet1.Range("J" & i), Sheet2.Range("J:AV"), 39, False)
'Vlookup to add  Country to Country column AT based on Mapping Table sheet 4
Sheet1.Range("AT" & i) = Application.VLookup(Sheet1.Range("G" & i), Sheet4.Range("A:B"), 2, False)
'Vlookup to add Theater to Theater column AU based on Mapping Table sheet 4
Sheet1.Range("AU" & i) = Application.VLookup(Sheet1.Range("G" & i), Sheet4.Range("A:C"), 3, False)

If Err.Number = 0 Then
Else
End If


Next



 'Adding Formula for Commit + X Column AS for Conf Call Analysis file
  Range("AS2").Formula =     "=IF(C2=""Commit"",""Commit+X"",IF(B2=""X"",""Commit+X"",""""))"
  Range("AS2").Select
  Selection.AutoFill Destination:=Range("AS2:AS" & Number_Rows)




  '***********FORMATTING BELOW**************


 'Format Revenue column K - no decimal, 1,000 seperator.
  Columns("K:K").Select
  Selection.NumberFormat = "#,##0"

 'Format Forecast Close Date column P
  Columns("P:P").Select
  Selection.NumberFormat = "d/m/yyyy"

 'Format Focus List column AE
  Columns("AE:AE").Select
  Selection.NumberFormat = "d/m/yyyy"

 'Format % Chance column AF
  Columns("AF:AF").Select
  Selection.NumberFormat = "0%"

 'Format cells with Dates as titles to dd-mm rather than long date
  Range("AB1:AC1").Select
  Selection.NumberFormat = "d-mmm"
  Range("AI1:AP1").Select
  Selection.NumberFormat = "d-mmm"


 'Add Data Validation to Allocation Status column
  Columns("AG:AG").Select
  With Selection.Validation
    .Delete
    .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
    xlBetween, Formula1:="=_Allocation"
    .IgnoreBlank = True
    .InCellDropdown = True
    .InputTitle = ""
    .ErrorTitle = ""
    .InputMessage = ""
    .ErrorMessage = ""
    .ShowInput = True
    .ShowError = True
End With


 'Sorting by Description A-Z, Business Manager A-Z and Revenue $ Largest to    Smallest
  Sheet1.Sort.SortFields.Clear
  Sheet1.Sort.SortFields.Add Key:=Range("C2:C" & Number_Rows _
    ), SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:=xlSortNormal
Sheet1.Sort.SortFields.Add Key:=Range("H2:H" & Number_Rows _
    ), SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:=xlSortNormal
Sheet1.Sort.SortFields.Add Key:=Range("K2:K" & Number_Rows _
    ), SortOn:=xlSortOnValues, Order:=xlDescending, DataOption:=xlSortNormal
With Sheet1.Sort
    .SetRange Range("A1:AU" & Number_Rows)
    .Header = xlYes
    .MatchCase = False
    .Orientation = xlTopToBottom
    .SortMethod = xlPinYin
    .Apply
End With


 'Hide Columns Quarter AA,Primary Partner OO, Reporting Product Type TT, Product Line VV, Opportunity Source Code QQ
 Columns("A:A").Select
 Selection.EntireColumn.Hidden = True
 Columns("O:O").Select
 Selection.EntireColumn.Hidden = True
 Columns("T:T").Select
 Selection.EntireColumn.Hidden = True
 Columns("Q:Q").Select
 Selection.EntireColumn.Hidden = True
 Columns("V:V").Select
 Selection.EntireColumn.Hidden = True


 'Colours Today column AD yellow
  Columns("AD:AD").Select
With Selection.Interior
    .Pattern = xlSolid
    .PatternColorIndex = xlAutomatic
    .Color = 65535
    .TintAndShade = 0
    .PatternTintAndShade = 0
End With


 'Colours Allocation Status column AG blue
  Columns("AG:AG").Select
With Selection.Interior
    .Pattern = xlSolid
    .PatternColorIndex = xlAutomatic
    .Color = 15773696
    .TintAndShade = 0
    .PatternTintAndShade = 0
End With


  'Bold Headings in row 1
   Rows("1:1").Select
   Selection.Font.Bold = True


 'Adding Conditional Formatting Order Number column J, to highlight all duplicate values so that all oppts that have more than one row are red.
  Columns("J:J").Select
  Selection.FormatConditions.AddUniqueValues
    Selection.FormatConditions(Selection.FormatConditions.Count).SetFirstPriority
Selection.FormatConditions(1).DupeUnique = xlDuplicate
With Selection.FormatConditions(1).Font
    .Color = -16383844
    .TintAndShade = 0
End With
With Selection.FormatConditions(1).Interior
    .PatternColorIndex = xlAutomatic
    .Color = 13551615
    .TintAndShade = 0
End With
Selection.FormatConditions(1).StopIfTrue = False



 'Adding last updated date
  Sheet3.Range("J1") = Date


 'Allows screen to refresh at the end
  Application.ScreenUpdating = True


 'Msgbox to advise when macro is complete.
  MsgBox ("File is now updated.")


  End Sub

I have figured out a number of work arounds, however, these slow down our productivity, and the error can comeback later on in the day. Can somebody tell me what is the likely cause of this problem?