Corrupt Photos

After having recently enabled iCloud Photo Library on my Mac, I was scrolling back through the photos and noticed that several of them seem to have been corrupted at some point. The thumbnails show with various amounts of black area covering part of the photo:

And the photo itself displays in a peculiar manner:

All the corrupt photos display in a similar manner: top part of photo, little thumbnail on gray horizontal line, then more top part of photo. Portrait photos are the same except: right part of photo, little thumbnail on vertical gray line, then more right part of photo.

All photos are from a ~2 month span of time about a year back, and not all photos in that span are messed up (but most are). I confirmed with my iPhone (also connected to iCloud Photo Library with the Optimize option on) that this oddity is not just local to my Mac. I know that these photos once used to display normally, and I'm unsure what could've triggered the change. I'm hoping there's some way to fix these photos, and I'm also concerned that this may happen again to more of my photos. Anyone have any insight as to a possible cause or solution?