Apple Photos app corrupts images

I had a weird issue with at least one photo in Apple Photos recently (possibly more that I haven't found) where the photos app showed the image, but I couldn't export it - like it was only a preview. I've upgraded my photos database over many release so I don't know if that's a part of it, the photo in question was from 2018 or so

See if you can File->Duplicate Photo it first.