Word 2013 Problems with Large Document

Hello - I am the IT guy for my company and we are having issues with a few large documents (docx) as of late. I have attached the document in question for your viewing. I am not an expert in troubleshooting MS Word issues but I am savvy when using it on a daily basis. The docx is about 5MB loaded with tables, equations, graphics, etc... The end user does alot of copy and pasting from other Word documents as well as copy and pasting from within the same document. After 10 minutes of doing just this and multiple saves, I have noticed the name of the document changes from the actual name to "~W74xxx". Now as far as I know, that's the name of a temporary document. With every save after this, it changes the name the last 4 characters of the document in the same temporary file format. So as the end user keeps saving, they don't realize that the original document they think they have been saving, is not saving.
There is clearly something funny going on within the text, tables, or equations of this document that is causing us so many problems.

I beg you, please help or point me in the right direction! Any help is appreciated at this point!! Thank you!

Chris
Problem-Document.docx