Hello folks, I have this weird Preview bug. I'll let this video explain it better. https://www.youtube.com/watch?v=C6MKoyX0N3c Here are some notes: - I have sent the same photos used on this troubled mac to another mac to test them out, and they worked perfectly on the other mac. - Sometimes it works, and sometimes it doesn't using the same file. I have no idea why. - On this same mac, I used to be able to edit photos without any problem before upgrading to Yosemite. Your insights will be much appreciated. Thank you.