Creating Word Document using MailMerge

We have word documents set up as templates with merge fields. We use the template and merge data and save the created word document. When you try and open the word document we get a message stating:
We're sorry. We can't open *filename* because we found a problem with its contents.
If we click OK we get the message
Word found unreadable content in *filename*. Do you want to recover ...
If we click OK the document opens. You can then save it and now it can be opened without getting the errors.

Dim doc As Document
 doc = New Document(*path to template*)
doc.MailMerge.Execute(New String() {"OrderTitle"},New Object() {sOrderTitle})
doc.Save(*save path*, SaveFormat.Docx)

Thanks for your help.

@vaughnrk

Could you please ZIP and attach your input, problematic and expected output documents here for testing? We will investigate the issue and provide you more information on it.