When I see your output specs, I can't help but wonder if the stutter you are seeing is an encoding problem, or a playback problem.
What sort of stutter are you experiencing?
If there's a stutter in the video / encoding process, it should be visible also if you skip through the video frame-by-frame in your NLE of choice. Is that the case? Because if so, we're looking at a blending / interpolation problem.
However, whta I'm thinking is that this might be a playback issue rather than an encoding problem.
What hardware and software are you using to play this UHD HEVC video?