Could it possibly be that it wasn't the drive, but maybe the import application?
https://news.ycombinator.com/item?id=45274277 (Apple Photos corrupts images on import - images truncated)
https://news.ycombinator.com/item?id=45274277 (Apple Photos corrupts images on import - images truncated)
i either copied them with $cp -ar or $rsync -a
then distinctly remembered diffing each drive against each other with $diff -qr <drive1> <drive2>