If these authors are registered users (and not additional authors or the articles have been created by import), this solution might help:
If you are still using OJS 2.x, I remember there was a problem that caused authors to be duplicated if an article created by XML import had its metadata edited from the backend. That caused the author(s) of that article to be duplicated from the other authors, which meant that every article by them had to be clicked “edit metadata” and then “save”. However, this only appeared with some language settings and may well have been caused by the import XML file in the first place.