I was importing my photos from my iPhone to my MacBook running El Capitan, and I got errors saying some files were in an unrecognised format, and some pictures turned out completely weird.
What's sad is that the Photos app though that the pictures got successfully imported (apparently there was no integrity check), and so it reported back to iPhone that it could delete the photos after the "successful" import (according to the checkbox in the import dialog.)
Guess I'll have to manually delete each photo on the iPhone after manually checking that all photos are in fact imported successfully now...