A family of Microsoft word processing software products for creating web, email, and print documents.
It appears to be a bug in the XML that defines the ISO 690 citation style. When one citation source doesn't contain any text, the style applies bold format to the entire paragraph instead of just the (missing) author name -- and then continues to do that to all the bibliography entries that follow, regardless of whether they contain valid author names. Although the bold formatting can be manually removed from the whole paragraph and then manually applied to just the author names, those changes will disappear if you update the bibliography field (F9).
I demonstrated this for myself by editing the citation source of entry 69, adding a fake author name "SG" but otherwise leaving the source intact. Updating the bibliography field resulted in bold author names in entries 69 and 70. However, because entry 71 has no author name in its source, that entry and all the ones after it remained all bold. As far as I can tell, though, trying to use a space or a nonprinting character as the fake author name is not successful.
Unfortunately, I don't have the knowledge needed to correct the XML in the ISO690.XSL file.