Errors during Export to HTML

I’m trying to export all my content from Scrivener to HTML.
I do the action on the left, then get the error on the right:

Alt-link: http://i.imgur.com/r0lrSty.png

It seems like many files are exported, but I’m not sure if there’s stuff being missed, and am worried about not having a full backup.

Any ideas? Thanks for reading!