Had a private message with deceptikon about this earlier today.
Certain older posts have invalid characters that didn't successfully make it through the migration off of vBulletin. The fully rendered version of the post was "faked" and there is no raw version that exists.
Essentially, it took hundreds upon hundreds of hours to rebuild the articles during the migration process. At the end of the day, we ended up with all but a couple hundred, which became an acceptable loss for the time.