I've just upgraded to Sierra and preview has some odd behaviour when viewing photos. When I first open a photo it opens fine in the normal size window, however if I then enlarge the window to fill the screen, either using the green expand button in the top left corner, or using snap to fit with bettersnap the photo is ever so slightly zoomed in and doesn't fit vertically. Pressing CMD+9 to fit doesn't work initially, however if I press CMD+0 to view full size and the CMD+9 to fit to screen it does then fit to screen. Has anyone else noticed this and know of a fix as it's very frustrating? I'm running a late 2011 MBP with hi-res (non retina) display. Any help appreciated.