I have noticed an issue when I resave an image that has an uppercase suffix (.JPG) from photoshop (which is currently set to save as lowercase .jpg) using the same filename. Admittedly I expected the original image to be overwritten by photoshop but that's by the by. I then noticed that the new image won't show in an already open contact sheet until I go to the finder and delete the original image then close and reload the contact sheet. Refreshing and rescanning from within PM doesn't seem have any effect.