Word Templates Opening Multiple Times

Several times a day I click on a ribbon button that runs the command:

Sub CreateInvoice(control As IRibbonControl)

Documents.Add "000-Merge Tools Invoice.dotm"

End Sub

and have been doing so for more than 15 years over which time I have moved from probably Office 2010 up to now Microsoft 365, without experiencing the issue that you mention.

While I usually have no reason to save the documents so created as Word documents (as I save them in PDF format) I have just now saved one as a Word document (.docx) that I have closed, re-opened. closed, restarted the computer and re-opened the document and in each case, after opening the document and going to the Developer Tab > Document Template, the template that is attached to the document is the one from which it was originally created, as shown by the following screen shot

Likewise, in the Visual Basic Editor, the  Project for the document contains a reference to the template from which it was created

Can you zip up a copy of the template with which you experience that issue and post it here, or send it to me at mergetools [atsymbol] gmail dot com and I will investigate the issue.