Hey guys, So I recently got my new 5K iMac 2017. Everything is fine except iTunes video playback seems to be choppy. Every couple of minutes there will be a period of 30 seconds of what appears to be low frame rate video playback. Audio is fine. I do not have this issue with my 2016 Macbook Pro or 2010 Mac Pro. If I connect a second display to my 2017 iMac, I do not have the issue either. Is there something I can do to make playback more smooth on the built in display? Is this a common issue, or is something else going on? Thanks.