In some cases you may end up with duplicate tags. To resolve this you can merge the tags together.
To merge people, navigate to the 'Tags' screen inside the 'Explore' tab and tap the person you wish to merge.
Tap the '•••' button in the top right and choose 'Merge Person'.
Select the person you would like merge into from the list which is displayed and tap 'Next'. You will then be presented with the 'Merge Screen'.
Choose which tag you wish to keep and then hit 'Done'. This operation cannot be reversed so please complete this with care.