Run-time error 6 overflow

Hi all,
I seek help to fix the below coding... I took over this spreadsheet from a former colleague. It was running smoothly for the past 3 months until now. Nothing has changed, in the files nor the code.
The error Run-time error 6 overflow comes up on the highlighted part of the code below and I am not sure how to fix it. Someone please help? MUCH appreciated!!!

Sub Output() 'Exporter

Dim thisWB As Workbook
Dim opWB As Workbook
Dim autoWS As Worksheet
Dim opWS As Worksheet
Dim valS As String
Dim opArr() As String
Dim coll1 As Collection
Dim coll2 As Collection
Dim coll3 As Collection
Dim coll4 As Collection
Dim coll5 As Collection
Dim x, y, z As Integer
Dim lRow1, lRow2 As Long


Set thisWB = ThisWorkbook
Set autoWS = thisWB.Sheets("AUTOMATION")

Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual

For x = 2 To 50

    If Not autoWS.Cells(x, 1).Value = "o" Then GoTo skip
    If Not autoWS.Cells(x, 2).Value = "y" Then GoTo skip
    
    Set coll1 = New Collection
    Set coll2 = New Collection
    Set coll3 = New Collection
    Set coll4 = New Collection
    Set coll5 = New Collection
    
    For y = 4 To 71 Step 5
    'set colls
        If Not autoWS.Cells(x, y).Value = "" Then
            coll1.Add autoWS.Cells(x, y).Value
            coll2.Add autoWS.Cells(x, y + 1).Value
            coll3.Add autoWS.Cells(x, y + 2).Value
            coll4.Add autoWS.Cells(x, y + 3).Value
            coll5.Add autoWS.Cells(x, y + 4).Value
            If y = 4 Then
                ReDim opArr(0)
                opArr(0) = autoWS.Cells(x, y).Value
            Else
                ReDim Preserve opArr((y + 1) / 5 - 1)
                opArr((y + 1) / 5 - 1) = autoWS.Cells(x, y).Value
            End If
        End If
    Next y

Sheets(opArr).Copy
Set opWB = ActiveWorkbook

Dim FName As String
FName = InjectDate(autoWS.Cells(x, 3).Value) 'set filename

If Not InStr(1, FName, ".xlsm") = 0 Or Not InStr(1, FName, ".xlsb") = 0 Then 'if filename contains .xlsm or .xlsb then import vb & assign buttons
    ImportVB.AddBas
    ImportVB.AssignButtons
End If


    For z = 1 To coll1.Count
    opWB.Sheets(coll1(z)).Activate
        If coll2(z) = "y" Then

            opWB.Sheets(coll1(z)).Range("A1:" & LastColumn(coll1(z), "1") & LastRow(coll1(z), "A")) = opWB.Sheets(coll1(z)).Range("A1:" & LastColumn(coll1(z), "1") & LastRow(coll1(z), "A")).Value
            

        End If
        If coll3(z) = "y" Then
            Selection.AutoFilter
            ActiveSheet.Range("A1:" & LastColumn(ActiveSheet.Name, "1") & LastRow(ActiveSheet.Name, "A")).AutoFilter Field:=coll4(z), Criteria1:=coll5(z), Operator:=xlAnd
        End If
        ActiveSheet.Cells(1, 1).Select
        If coll3(z) = "h" Then
            opWB.Sheets(coll1(z)).Visible = False
        End If
    Next z

          'save & close output file
If Not InStr(1, FName, ".xlsm") = 0 Then 'if the filename contains ".xlsm" (NOT =0 means found)
    opWB.SaveAs Filename:=FName, FileFormat:=xlOpenXMLWorkbookMacroEnabled 'save as .xlsm
Else
    If Not InStr(1, FName, ".xlsb") = 0 Then 'if the filename contains ".xlsb" (NOT =0 means found)
        opWB.SaveAs Filename:=FName, FileFormat:=xlExcel12 'save as .xlsb
    Else
        opWB.SaveAs Filename:=FName, FileFormat:=xlOpenXMLWorkbook 'save as .xlsx
    End If
End If

Application.DisplayAlerts = False
opWB.Close
Application.DisplayAlerts = True

skip:

Next x

Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic

End Sub