VBA筛选后获取首个可见行报错求助（原代码曾正常运行）

原本运行正常的VBA代码，用于筛选数据区域后获取首个可见行的行号，对比currentregion、SpecialCells等方法后选择SpecialCells实现。

仅将wsa变量提前声明后，对同一数据源执行两次筛选操作时，原本正常的语句：

a = wsf.AutoFilter.Range.Offset(1, 0).SpecialCells(xlCellTypeVisible)(1).Row

开始抛出错误1004 - 应用程序或对象定义的错误。相关数据源及wsf的定义均未改变，理论上变量声明位置调整不应产生影响。

多方排查无果，尝试其他方法后虽不再报错，但返回的行号始终为1（测试预期应为48000左右），而下方功能完全相同的wsa相关语句却运行正常。两个文件均为xlsm格式，工作表设置与筛选操作均无误，恳请协助排查。

相关代码 #

Dim deb As Date: deb = Now()
Dim owa As Workbook: Set owa = ThisWorkbook
Dim ows As Worksheet: Set ows = owa.Worksheets("Feuil1")
Dim PremAg As Range: Set PremAg = ows.Range("w2")
Dim LastAg As Range: Set LastAg = ows.Range("w" & ows.Cells(Rows.Count, "w").End(xlUp).Row)
Dim RngAg As Range: Set RngAg = ows.Range(PremAg, LastAg) 'full list of criterias I'll apply

Dim CellClient As Range
Dim CellFact As Range
Dim Agence As String
Dim wba As Workbook 'file with clients' info
Dim wsa As Worksheet 'relevant sheet 
Dim RngClient As Range 'full list of clients' IDs according to client file
Dim RngFact As Range 'same but for invoices file
Dim Poubelle As Range 'Trash that stocks used up invoices to then delete them once I used them
Dim n As Integer
n = 0
Dim wbf As Workbook 'invoices file
Dim wsf As Worksheet 'relevant sheet for invoices
Dim a As Integer
Dim b As Integer
Dim c As Integer
Dim d As Integer

Set wbf = Workbooks.Open("C:\Users\QNS691\OneDrive\Documents\Excel\par agence 5\facts torturées2.xlsm")
Set wsf = wbf.Worksheets(1)

Set wba = Workbooks.Open("C:\Users\QNS691\OneDrive\Documents\Excel\par agence 5\full.xlsm")
Set wsa = wba.Worksheets(1)

Application.DisplayAlerts = False

For Each CellAg In RngAg

    wsf.Range("A1").AutoFilter field:=7, Criteria1:=CStr(CellAg) 'filter works well
    a = wsf.AutoFilter.Range.Offset(1, 0).SpecialCells(xlCellTypeVisible)(1).Row 'and then there's this little thing that worked just fine but then threw a fit
    b = wsf.Range("g1").End(xlDown).Row
    
    wsa.Range("A1").AutoFilter field:=7, Criteria1:=CellAg
    c = wsa.AutoFilter.Range.Offset(1, 0).SpecialCells(xlCellTypeVisible)(1).Row 'while that one works ok...
    d = wsa.Range("g1").End(xlDown).Row
    
    Set RngFact = wsf.Range("g" & a, "g" & b)
    
    Set RngClient = wsa.Range("g" & c, "g" & d)
            
    For Each CellClient In RngClient
        n = 0
        ag = wsa.Cells(CellClient.Row, 7)
        For Each CellFact In RngFact
            If CellClient = CellFact And ag = wsf.Cells(CellFact.Row, 7) Then
                n = n + 1
                If Poubelle Is Nothing Then
                    Set Poubelle = CellFact
                Else
                    Set Poubelle = Union(Poubelle, CellFact)
                End If
            End If
        Next CellFact
        
        If Not Poubelle Is Nothing Then
            'Debug.Print Poubelle.Address
            Poubelle.EntireRow.Delete
        End If
        Set Poubelle = Nothing

        If n > 1 Then
            wsa.Cells(CellClient.Row, 9) = n
        End If
        
    Next CellClient
    
    wba.Save
    wbf.Save
Next CellAg
Application.DisplayAlerts = True
MsgBox y & Chr(10) & deb & " " & Now()

End Sub

内容的提问来源于stack exchange，提问作者ThismaddePro