A Damaged Word file

while analyse the file using next two methods, an exception is throwned.
method:

wrong message:

we know the file is damaged,but the Part A wants to know why the file is damaged or what’s wrong with the file,an how to avoid the damage.
Here is the file:
重点难点技术保障措施.docx (155.0 KB)

@Melancholy DOCX document consists of zipped XML files. You can unzip your document and make sure the document.xml is not valid XML file. This causes the exception:

System.Xml.XmlException : Invalid character in the given encoding. Line 2, position 50342.