Let me get this straight, you've got an error about a broken link, and you say that one of the changes you made to your docx file was changing links, and yet you conclude that the problem must be in calibre?
And as Eli said, dont export to html, use docx directly:
http://manual.calibre-ebook.com/conv...word-documents
Finally, if you want detailed help you need to follow the instructions here:
https://www.mobileread.com/forums/sho...d.php?t=186697