I went into the folder where the photo was that it kept returning to, and I have now been able to get it to snap to a different photo.
Here's what seems to trigger it the most reliably.
Beforehand:
Have previously cropped a photo from a folder somewhere and saved the crop to that same current folder.
Then to trigger it:
1) rate a new photo for the first time
2) then crop it, and save crop to the current folder
3) When crop is finished being saved, PM snaps the preview window to one of the previously cropped photos (could be in a totally different folder, or might be in the same one).
With earlier versions of PM, when a crop is saved in the current folder, I don't think anything happened. It just went into the same folder and then would be next in the photo stream of that folder. I had to use the next arrow or rate the photo in order to advance to the crop. It never tried to automatically jump to the cropped photo that was saved. And definitely never automatically jumped to some other previously cropped photo.