OK, if you're using process designer for help desk, a number of the out of box HTML notifications in the Incident Workflow notify the contact.name but are not correctly labeled. Check every HTML notification in your workflow ruleSets, including the out of box ones. I specifically recall one which was labeled that it notified the ticket owner that actually notified the contact.name. There may be more.
Also, the out of box rulesets notify the requested.by ID repeatedly. These could be the source of a duplicate.