Run-time error 1004: this action won't work on multiple selections

I have posted this question before but it was for sharepoint. I thought the error was due to sharepoint but now the file has been moved to a local folder yet it still happens sporadically. I am starting it as a new question hoping it will get answers.


The routine is to copy data from some child workbooks and paste to the parent file. The error happened on the line pastespecial. The error happens once in a while so I am wondering if anyone has had similar experience as I am not sure if it's the routine itself or an excel bug? Any help appreciated!!

Set mFSO = New FileSystemObject
mFolderPath = ThisWorkbook.Path

mFolderPath = Replace(mFolderPath, "/", "\")
mFolderPath = Replace(mFolderPath, "http:", "")

mFileName = Dir(mFolderPath & "\")
Set mWBD = ThisWorkbook
Set mWSD = s_Data
mFileName = Dir(mFolderPath & "\")

Set mWST = Worksheets.Add
lc = mWSD.Range("a3").End(xlToRight).Column
mWSD.Range("a3", mWSD.Range("a3").End(xlToRight)).Copy
mWST.Range("a3").PasteSpecial xlPasteValues
Application.CutCopyMode = False

i = 0
mFileName = Dir(mFolderPath & "\")
Do
    If InStr(mFileName, "_") <> 0 Then
    i = i + 1
        lrT = mWST.Cells(Rows.Count, "a").End(xlUp).Row
        mFilePath = mFolderPath & "\" & mFileName
        
        If bFileOpen(mFilePath) Then
            bOpen = True
        Else
            bOpen = False
        End If
        
        If bOpen = False Then
             Set mWBO = Workbooks.Open(mFilePath)
             Set mWSO = mWBO.Worksheets("Data")
             
             If mWSO.FilterMode Then
                 mWSO.ShowAllData
             End If
             
             lrO = mWSO.Cells(Rows.Count, "a").End(xlUp).Row
             lcO = mWSO.Range("a3").End(xlToRight).Column
             mWSO.Range("a4", mWSO.Cells(lrO, lcO)).Copy
             
             With mWST
                .Activate
                .Range("a4").Select
                If lrO > 3 Then
                    If lrT = 3 Then
                        .Range("a4").Select
                        Selection.PasteSpecial Paste:=xlPasteAll, Operation:=xlNone, SkipBlanks:=False, Transpose:=False
                    Else
                        .Cells(lrT + 1, "a").Select
                        Selection.PasteSpecial Paste:=xlPasteAll, Operation:=xlNone, SkipBlanks:=False, Transpose:=False
                    End If
                End If
            
                Application.CutCopyMode = False
                mWBO.Close False
            End With
        End If
    End If
    
mFileName = Dir()
Loop Until mFileName = ""   
    
        
End With
    Set mWBO = Nothing