Shaky video

I’ve been using Kodi on Linux for several years with no problems. But I recently got a new laptop, and now I’m getting juddery video. Not all the time, but for a few seconds every minute or so, and it’s very annoying. Ther GPU is generally running at about 80% during playback, but I never looked at it on previous machines, so I don’t know if that’s a problem. I’ve played around with the VDPAU and VAAPI settings, but I’m not sure what I’m doing, and I’ve not seen any improvement.

Can anyone suggest anything else I can try? Thanks.

Kubuntu 17.04
8-core Intel I7-770 CPU @ 3.6GHz
8GB RAM
3840×2160 screen
NVIDIA GeForce GTX 1070 GPU (Gallium 0.4)
OpenGL 3.0 Mesa 17.0.3