Photos still losing face tags, any help?

As to pet faces: Apple has announced that the pets will be also recognized in the next system version macOS 14 Sonoma. We will be seeing an album "People & Pets".

Just to support the advice given by Richard - it is really the best way to save the names. I have used keywords to save the names of the people in all photo managers offered by Apple - iPhoto, Aperture, and now Photos. It helps to recognise lost faces immediately with smart albums, but even more important, it helps to save the named faces when migrating to a different photo manager. My named faces survived the migration from iPhoto to Aperture to Photos. And the face names will be embedded in the exported photos, when I export an edited version.

I started to add the names as keywords for a different reasons, because the names of the people are not shown in the Info of a photo, just a cute thumbnail of the face, that is even harder to recognise than the face in the picture. And even in the People album Photos has shown just a short name, not the full name The silly short names did not help to find out quickly the name of a person, so I looked for a useful way to write the full names into the Info.

I elaborated a bit on this in this user tip:

How to use Keywords to Back Up the Named Faces in Photos and Improve the Search for People … - Apple Community

But I am a bit worried about your experience with losing face tags soon after adding them. There must be something wrong with the Photos Library or the location of the Photos Library.

I have seen a lot of vanishing face tags, but only for obvious reasons:

• After migrating from iPhoto to Aperture and from Aperture to Photos
• After a major system upgrade, that improved or changed the face recognition algorithm and Photos had to repeat the faces scan
• After turning on iCloud Photos and having inconsistent names on my iCloud devices
• After restoring a library from iCloud - then the manually added faces do not all come back
• After editing a photo

Make backup copies of the Photos Library before doing anything, that might modify the People album, as pointed out in the list above.

If named faces keep vanishing out of the blue, I recommend to contact Apple Support. There must be some additional problem that needs identifying, perhaps a reason for frequent crashes.

And you may want to write feedback to Apple to point out, that many users need the People album to look up the names of people. It is also my main reason to add the names to the faces.

The Apple developer team seems to see the People album as a way to retrieve photos quickly, just the photos of people we are meeting most frequently and who are in our Contacs. I do not need to tag the faces of people I am meeting everyday, with hundreds of photos of them in my library. I need to tag the faces of people in old scans of family photos, where I had to ask someone to identify the people, because I have never met them.

Or to remember the names of people I have met only once in my life. Most of the names in my People album are not in my Contacts.

Many of us use keywords for identifying people and animals in pictures. I load all the "Aunt Bertha" pictures using a smart album with the specification "Person" "includes" "Aunt Bertha." I "select all" and assign the keyword "AuntBertha" to all those pictures. I do the same for "Uncle Walter" and all the rest. So I use the face tags to help me assign keywords. I also assign the keywords to pictures that aren't tagged by face recognition, including pets. I mostly do not manually assign face tags-- the exception is group photos where an alphabetical list of included people just isn't enough information.

Keywords will be included in the picture's metadata when it's exported with File>Export>Export nn Photos. Face tags are not. Keywords will survive major upgrades.

So keywords are the major identifier; face tags are used mostly to help assign keywords.

Yes I continue to have this issue as well and it has existed for multiple years. I believe that it is somehow connected to using iCloud Photos and data from the server somehow over writing the tags places on the local machine but I have not been able to prove that. It is a frustrating bug that I wish there was a way to get Apple to prioritize fixing it. I have tried with each new update of Photos to tag some of the faces again only to see them disappear some time later.