I have the same exact issue with my AU8000, I have a comcast 4K cable box. It turned out that the tv does not like 4K 60 Frames per second or 1080p 60 frames per second. I forced the cable box on 4K 30 frames per second and it cleared it up. Its a total joke, I cant figure out if the tv is the actual issue or a combability issue with comcast. I would be interested to know if you try this and it works for you. As an example CSI Vegas was the biggest offender of this stuttering. The other weird thing was if I watched the same program on comcast ondemand it would be as smooth as could be using 4K 60 frames per second on the cable box.