"Cannot find central directory"

I am trying to translate a single word document from Japanese to English using SDL Trados Studio 2017 Freelance.
After the stage of selecting the TM I wish to use, I get the error message "Cannot find central directory".
Copying the content of the original file into a new Word document does not help.

For reference, the document contains footnotes, which almost always causes me problems, although I have never seen this error message before.

I suspect I could solve this issue by deleting the footnotes, translating the document, then adding them again manually, but I would really rather solve this issue more elegantly and efficiently.