I eventually just decided to give a name to the second collection. My dog’s name is Daisy Mae. The name I gave to the second collection will make sense once you see the “face circles” in that collection. I have no idea what Photos thinks it’s doing, or why it won’t let me “fix” this problem by merging the collections. Just look at this mess…

https://files.mastodon.social/media_attachments/files/111/182/720/576/435/852/original/4b7a9011d81218d6.png

https://files.mastodon.social/media_attachments/files/111/182/722/313/291/493/original/670d5413fdc1d498.png

https://files.mastodon.social/media_attachments/files/111/182/721/326/565/045/original/6bd11299acb1c9f3.png