xg1v4-a Frame rate issue

I was wondering if anyone else has seen this issue? Maybe a Comcast employee can reply. I have a Samsung au8000 4K tv. The best available output on the cable box is 4K 60 fps. On certain programs the video stutters and jitters pretty bad. It does this on 1080p 60 fps also. If I switch to 4K 30 fps it is as smooth as can be. WhAts going on? I have all motion enhancements shut off on my tv. To me seems like a cable box compatibility issue. It only happens on certain hd channels with certain programs. CSI Vegas as an example. If I play the content through on demand and have the box set for 4K 60 fps it does not stutter at all.