Word VBA function InsertFile is now failing on all builds from 15427.20194 Aug 3, 2022 and later

We have a product that assembles custom templates that has been around for about 20 years that operates on a library of about 1 million Word .docx format templates.  With users across the world.  Its been in use on every version of Word since 2003 (currently only supported on all versions of Office 365 but it also still works on Word 2010).   We use the Word VBA function InsertFile to append pages together to create custom documents from the template library.

Recently all of our installations started failing with the InsertFile function returning error 5097 - "Word has encountered a problem".  And customers have started reporting the same error.

We traced it down to being introduced in the Aug 3 Build of Word and verified it on multiple computers (both Windows 10 and Windows 11).   If we roll back our Word builds through the last 7 builds we found that in every case the June 14, June 29, July 6, July 18 builds of Word work fine.   But all 3 builds after that which are Aug 3, Aug 9 and the current Aug 31 fail.

Something appears to have been recently broken by Microsoft in the Aug 3 Build that causes the Word's InsertFile function to fail.    This happens on almost all of our Word .docx template we have tested.    But when inserting the file via the Word toolbar's Insert > Text From File > browse to the file it works.  But it always fails now when calling the InsertFile function via VBA.   Again, this is not a new macro or templates.  This code has been in use for almost 2 decades and the templates have been in use for for many years.   Its only since the recent builds of Word in the last month that installations are now starting to fail everywhere.

This zip file linked below contains the macro vba test function and some example files to reproduce the problem.

InsertFile Failure Test

When we save those templates that are failing to insert as legacy Word 2003-2007 .doc files they do insert without failing.   And if we save them in Word 2003-2007 XML or as an OpenDocument .odt file they insert correctly.   But if we save them as Word XML .xml or Strict Word XML .xml they also fail.  So there is nothing corrupt in the files, it appears to be inserting current format files of various file formats are failing, but saving those failing files as legacy formats they insert correctly.

How do we submit this problem to Microsoft's Office 365 team as a bug report? This is a serious problem that breaks our product and requires us to have everyone roll back their Office 365 to the July 18, 2022 build and we're in the process of having to update our product to provide instructions when the error occurs on how to roll back Office 365.

The code in the test script is also here. But it needs the .docx files from the ZIP file to operate on.

Sub InsertTest()

Dim DocRng As Range  
Dim FileToInsert As String  
Dim SourceFile As String  
Dim MsgStr As String  
Dim MsgResult As Long  
          
On Error GoTo ErrHandler  
 
SourceFile = "c:\temp\CoverLetter.docx"  
  
FileToInsert = "c:\temp\ExecSummaryA.docx"      ' This file fails to insert  

' FileToInsert = "c:\temp\ExecSummaryB.doc" ' This file works (this was the ExecSummaryA.docx Saved As a .doc file in Word 2003-2007 format)
' FileToInsert = "c:\temp\AccessoriesA.docx" ' This file fails to insert
' FileToInsert = "c:\temp\AccessoriesB.doc" ' This file works (this was the AccessoriesA.docx Saved As a .doc file in Word 2003-2007 format)

Documents.Open FileName:=SourceFile  

ActiveWindow.ActivePane.View.Type = wdPrintView  
  
Set DocRng = ActiveDocument.Content  

DocRng.Collapse (wdCollapseEnd)  
              
DocRng.InsertFile FileName:=FileToInsert, Range:="", ConfirmConversions:=False, Link:=False, Attachment:=False  

Exit Sub  
  

ErrHandler:

MsgStr = "Error: " & Err.Number & " - " & Err.Description  

MsgResult = MsgBox(MsgStr, vbSystemModal + vbMsgBoxSetForeground, "Insert Error")  

End Sub