Word Automation - locking files

Now that's strange. A client is using some custom-made Word Automation from Navision that's been working for years and now it's broken, maybe due to a Word/operation system/whatever upgrade. The problem is that even though WordApp.Quit is called, the Word doc stays locked (even though it's not open) by that user. And the document is on a network drive, everybody is using that copy, so nobody else can use that automation function anymore.

I have a faint gut feeling that the whole stuff is badly written, because for mail merge I think one should use a .DOT, not a .DOC, but instead it's a .DOC that then gets modified by mail merge, printed, and then not saved.

But anyway, it worked for years. I think maybe the current versions of Word might be too strict about it - a modified document stays locked even if you close it without saving?...

Anyway, what I suggested to them to copy a copy to a local drive and use from there. I hope Word doesn't lock if it's the same user...

Any ideas?