Google-docs – limit on the length of a Google doc I can save as a Word doc

I have a 600-page document on Google Docs which I would like to save on my desktop as a Word doc, as a back-up.

I go to "File" then "download as" then "Microsoft Word" which is the common way of saving a document from Google to Word. My 600 pages are mostly text and contain about 1-2 photos per page. Unfortunately the first 48 pages are copied each time..

I wonder if perhaps there is a limit as to how much one can copy, and if perhaps 600 pages is too long? If that is not so, can you please advise how to fix this problem, and make a back-up on Word of the entire document.