When I upgraded the Co-Authors Plus plugin the author links broke. Basically the name was repeated twice, followed by quotation marks and a closing bracket, then the author's name again. All the names (but not the quotation marks and closing bracket) were links, but only the first instance of the name had the correct url.
It looked something like this:
AuthorFirstName AuthorLastNameAuthorFirstNameAuthorLastName"> AuthorFirstName AuthorLastName
Not sure if that makes any sense... I deactivated the plugin and installed the Co-Authors plugin instead, which apparently isn't being maintained anymore, but it works.