Have you cleaned up your duplicate records in a while? If not, it's a good thing to do on a regular basis, especially if you have a lot of new data being added to your database. Here's how:
Articles: https://trailblz.com/kb/?action=search&qq=dupe&cat=0&con=0
Video: https://www.youtube.com/watch?v=6Yue7DjNA_8