XML was designed from the beginning to be intolerant of errors. This decision adversely affects MS Word's corruption recovery. With one error in the document.xml subfile where all the DOCX file's text is stored, instead of a partial recovery, Word will stop and throw an error.
Savvy DOCX Recovery attempts to do precise surgery on corrupt Word documents to reorder or excise bad XML tags.
If this doesn't work, it uses the command line app xmllint first to attempt to repair corrupt XML...