I carefully arranged all my photos in the Group by None view so I had everything prioritized the way I wanted people to see it in the Carousel View. I switched to Group by Room to check a few things and decided I wanted to reorder a couple of photos within a given room. When I switched back to Group by None, I discovered that a whole bunch of my photos had been rearranged in the Group by None view after I'd changed them in the Group by Room view.
I realize I should do a screen recording or a series of screenshots and step through exactly how this worked. Quite frankly, it was so much effort to set up and fix that I'm not going to go through it again. I encourage you to check this, and I want other users to be aware that if you make ordering adjustments in the group by room view, be sure to double-check that your ordering is still the way you want it in group by none for the carousel.