Excel for MAC is crashing

[excelpunk]

Hello All,

I am trying to fix the following macro which I am trying to execute in MAC. It works/loops for sometime and then excel gets closed. My code below:

Set wb = ActiveWorkbook
Set ws = Sheet1
a = Sheet4.Cells(Rows.Count, "A").End(xlUp).Row
If a > 1 Then
    For b = 2 To a
        c = Sheet1.Cells(Rows.Count, "A").End(xlUp).Row + 1
        
        Workbooks.Open (Sheet4.Cells(b, "A").Value)
        Set wbb = ActiveWorkbook
        Set sh = wbb.ActiveSheet
        bb = sh.Cells(Rows.Count, "A").End(xlUp).Row
        
        wb.Activate
        ws.Select
      
        Range(Cells(c, 2), Cells(c + bb - 1, 4)).Value = Workbooks(wbb.Name).Worksheets(sh.Name).Range("A1:C" & bb).Value
        wbb.Close savechanges:=False
        
        Set sh = Nothing
        Set wbb = Nothing
        
        d = Sheet1.Cells(Rows.Count, "B").End(xlUp).Row
        Sheet1.Range(Cells(c, "A"), Cells(d, "A")) = Replace(Sheet4.Cells(b, "B").Value, ".txt", "")
    Next
End If
Application.CutCopyMode = False
ActiveWorkbook.Save