If you pause the video and go to the three dots on the right hand side, click ok, then click on where it says hd (1080p) change it down to 720p and it works without the stuttering.
i know this is a late reply, hope you’ve managed to sort it
2 weeks ago
A little bit late I know but I've created a short video showing how to solve the YouTube stuttering issue...
But why would any one want to downgrade a 4K and or 1080p video to 720p???
A better solution watch YouTube on another device!