Issues adding and removing faces in Photos on Apple M1 iMac

normanjx wrote: …Clicking onto the photo image first and/or after the face circle has been drawn does not seem to help in these cases.

What about adding the name, first? By the way, it works fine for me on Tahoe. So it's not the OS. Try this:

• Restart the computer (of course)
• Re-start in Safe Mode. This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this: 

           Start up your Mac in safe mode - Apple Support 

• Use another library if you have one, or make a small test Library with a few pictures in it and see if the same thing happens. You can create a new Library by closing Photos and then option-clicking on the Photos icon.
• Make a new user and see if the same problem recurs with it.  This is a bit harder, because a new user can't access a different user's stuff. You would need to temporarily move your Library out of your own user's Pictures folder up to the general "Users" folder. 
• Rebuild your Photos Library--close Photos and re-launch by option-command-clicking the app icon. If you use iCloud Photos, it’s possible that this will cause a re-sync that lasts long enough to make you nervous. I usually turn off wifi when I do this.

While placing names in the caption is an option, and in several cases I have done this (different use case) The Photos name facility is preferable for some of my projects.

If the names are important, then you should do both. See the article on names that I linked.

I shouldn't be hard for Apple to provide a more coherent workflow, possible using modifier keys (Option, Shift etc.) to make the facility work as I imagine most users would expect.

If you have suggestions for Apple, we can't help. Go here:

Feedback - Photos - Apple

normanjx wrote: Sometimes it works, but often when I tap "Add faces" from the info box, photos will create a face circle in the centre of the picture, but if I try to move it over the face I just get a thumbnail of the image.

It sounds like you're using Manual naming. This puts a circle at the center of the picture, and you are to move it over the face you want to name. This is not connected with the computer's face identification-- you can put the circle over a flower and name the flower, if you like.

The one problem we sometimes have is that the circle refuses to move, because Photos thinks we are still in the info window, and that we want to drag the picture there, or something like that. In that case we need to tap on the picture somewhere to let Photos know we mean it to switch its focus to the picture, and then we can move the circle. Or, we can just type the new circle's name first, and then move the circle. 

Manually naming a face doesn't affect how Photos chooses faces and identifies them. When you change "unnamed " to Charles, it helps Photos understand what a “Charles” face is. But manually adding a Charles circle only adds his face to his album. 

I also have an opposite problem. Photos sometimes recognises a face that I don;t want to identify. This can happen if there are strangers nearby or even a picture hanging on a wall. Again, Apple doesn't seem to provide a reliable way for me to remove a face circle that I don't want.

That's right. Unnamed will always be Unnamed. The best thing is to leave them alone.

Those of us working with this have learned not to depend on it too much. We use Keywords and Captions for names, and we use the the face names to help us with that. You may want to see this:

Saving Face Names for Genealogy - Apple Community