Column disappear when using advanced Filtering through VBA

Hi, I'm struggling to understand why after the first loop (Z=2) all of a sudden column A in WS ATT disappears. Worth adding that column M in WS L is a "dynamic" range (at first it contains 7 cells) in the sense that it shrinks with each loop (M2:M8, second loop: M2:M7 etc.). I can produce a sample, but maybe somebody see why my prob. is happening through this code?

For Z = 2 To 5
ThisWorkbook.Sheets.Add.Name = L.Range("M2").Value
        ATT.Range("A1:N100").AdvancedFilter Action:=xlFilterCopy, _
        CriteriaRange:=L.Range("A1:N2"), CopyToRange:=Sheets(Z).Range("A1"), Unique:=False
        L.Activate
        L.Range("M2").Select
        Selection.Delete Shift:=xlUp
Next Z