Word found unreadable content

[btam05]

When trying to open a .docx file created by this library, Microsoft Word sends the following error message: "Word found unreadable content in a.docx. Do you want to recover the contents of this document? If you trust the source of this document, click Yes"

The .docx file is fine and no data is lost, but I was wondering if there was a way to open it without the error message popping up

[totravel]

All characters must be in UTF-8 encoding.

[btam05]

I get the same error when trying to create a blank document. All my source files are in UTF-8 as well.