为什么此 Excel 宏获取运行时错误 4198？

问：

我正在运行一个宏，该宏使用excel中的各种字段填充Word模板书签。宏本身运行良好并生成字母，但每次我也会由于以下行而弹出运行时错误 4198：

wdDoc.SaveAs2 xlBook.Path & "\Letters\" & xlSheet.Cells(r, 1) & ".docx"

我不确定 VBA 哪里出了问题，因此非常感谢任何帮助。

谢谢

Sub LetterGenerator()

    Dim xlBook As Excel.Workbook
    Dim xlSheet As Excel.Worksheet

    Dim wdApp As word.Application
    Dim wdDoc As word.Document
    Dim wdTemplatePath As String

    Dim r As Long

    '// INSTANIATE EXCEL OBJECTS
    Set xlBook = ThisWorkbook
    Set xlSheet = xlBook.Worksheets("Sheet1")

    '// INSTANIATE WORD OBJECTS
    Set wdApp = New word.Application

    '// SET TEMPLATE PATH
    wdTemplatePath = xlBook.Path & "\Letters\letterDoc.docx"

    '// LOOP THORUGH EXCEL DATA ROWS
    For r = 2 To xlSheet.UsedRange.Rows.Count
    '// OPEN TEMPLATE
    Set wdDoc = wdApp.Documents.Open(wdTemplatePath, , True)

    '// LOOP THROUGH EXCEL COLUMNS
    For c = 2 To xlSheet.UsedRange.Columns.Count
        '// FILL BOOKMARK
        wdDoc.Bookmarks(xlSheet.Cells(1, c)).Range = xlSheet.Cells(r, c)
    Next c
    
      '// SAVE AS DOC
    wdDoc.SaveAs2 xlBook.Path & "\Letters\" & xlSheet.Cells(r, 1) & ".docx"

     '// SAVE AS PDF
    wdDoc.ExportAsFixedFormat xlBook.Path & "\Letters\" & xlSheet.Cells(r, 1) & ".pdf", wdExportFormatPDF


    '// CLOSE WORD TEMPLATE
    wdDoc.Close False
    
    '// RELEASE OBJECT
    Set wdDoc = Nothing
    Next r

    '// QUIT WORD
    wdApp.Quit

    '// RELEASE OBJECTS
    Set wdApp = Nothing
    Set xlSheet = Nothing
    Set xlBook = Nothing

End Sub

有人建议添加以下内容，但没有用：

Sub UpdateBookmark(doc As Word.Document, bookmarkName As String, replacementText As String)
    On Error Resume Next
    doc.Bookmarks(bookmarkName).Range.Text = replacementText
    On Error GoTo 0
End Sub