contacts added to iphone sometimes double

I have a user that has an I phone 6. We removed all his contacts since he was having some issues and made sure everything was correct. We then uploaded them into his Outlook email profile and added his business email to his phone. His contacts were fine. He started to add new contacts and some of them started to double. He said all he did was go to Contacts and add in the information. We can not figure out why some of them double up. He does have i Cloud on but it is full and has been so it has not been backing up since 2013 and he is aware of that. Could that still be the issue even though they are new contacts?