This is a mystery I'd like to solve if anyone has an idea: this .docx cannot be processed in Studio 2017 and there is no other explanation other than this error message. Someone else had a similar problem, I saw, and was able to process the document in Studio 2015, so I tried the same solution. It worked! After converting the file into .sdlxliff in Studio 2015, I was able to open it in Studio 2017 and continue processing it with no problems.
But I'd like to hear any ideas as to what might be causing the problem and what to do in the future if using Studio 2015 doesn't work? It's frustrating not knowing what kinds of issues are involved with this error message.
(By the way, I tried copying and pasting the contents of this file into a new .docx file but that did not work. I don't see any formatting issues in this .docx that aren't in its other 6 companion files, all created on the same day using the same methods and computer.)
Cheers and thanks!
Zakiya