Word's master document 'feature', if that's what you're using, is a known source of document corruption. See:
https://wordmvp.com/FAQs/General/Why...ocsCorrupt.htm
http://www.addbalance.com/word/masterdocuments.htm

To start a new chapter on a new page, you can do any of:
• insert a 'next page' Section break between them;


• insert a manual page break between them; or
• format the paragraph Style that starts each chapter with the 'page break before' attribute.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]