OK. I spent some time looking at this. I've discovered that this issue began around the same time that we started adding a single option (default value) to the extra field, "Photographer".
We used to not add any options (photographer's name) when creating the extra field, but rather made it an empty text field and then type the photographer's name in for every photo.
I also checked the categories where this issue appears (all of them since we started adding the default value) and there aren't multiple extra fields in any of them. Only the one extra field.
What is very odd is that this issue doesn't affect every photo in an individual category the same way. One photo displays the extra field info correctly but the very next photo might display the extra field info multiple items. And it might display the extra field info twice or 10 times. I simply can't find a pattern.
I've instructed my photo people to create the extra field as a drop-down menu for the photographer's name and include two options (not just one default value). This is nothing more than a shot in the dark, but perhaps if doing it this way doesn't create the issue, it might give you more information. We'll be publishing photos from a tournament next week, so we'll know how this shot in dark goes pretty soon.