I spent hours today using the facial recognition in the Photos app on my iMac, getting all my family organized by their face (obviously). I then started looking into if I had duplicate photos and used two pieces of software, PowerPhotos and Photos Duplicate Cleaner. I was able to remove a decent amount of duplicates but low and behold.. When I opened the Photos app after learning the duplicates, all of the facial recognition work I had done today was gone. I basically have to start from scratch. Any idea what could have caused this? I would like to pin point the issue, so I can avoid in the future. Any help is greatly appreciated!