I recently purchased a iMac retina 5k (Intel i7 4GHz, 16GB ram, 1TB Fusion, AMD R9 M290X 2GB) and I have been noticing that the interface stutters when changing wallpapers on my desktop. It doesn't happen every time but sometimes I am able to catch the transition and I can tell that even the mouse cursor stutters a bit till the wallpaper fully transitions to the next one. additional info: - I have an additional monitor attached running at 1920x1080 - The wallpapers are at 5k resolution (5120x2880) and change every 5 minutes (*only on the iMac not on the other monitor). Has anyone else noticed this? Other than this strange lag the system runs perfectly.