The issue I can see was he had the same contact several times in both his Outlook personal contacts as well as internal staff members which are also in the group contacts. On top of this the same contacts also existed in his iCloud several times. My recommendation would be to remove the syncing of Contacts (and delete from iPhone) for iCloud and rely on your Outlook contacts and Traffitech group contacts. That way they are always available via Outlook on your server login as well as on your device. If you do want/need to also use iCloud then I suggest you ensure each contact only exists once in either Outlook OR iCloud, not both locations. You can check iCloud contacts by signing in here: https://www.icloud.com/#contacts 

Other apps can sync contacts to your iPhone but I suspect this will be the main cause. Any issues or questions let us know.