My setup is a Ryzen 2700x with an Nvidia 1070ti.
I have sufficient bandwidth (200Mbps) and the video loads really fast. When I start playing the video everything seemingly runs Every five seconds there is a really minor tiny hiccup in both sound and picture. As I said, the video is already buffered up really well and these keep occurring every four seconds.
Here is a link to a 4K HDR video on YouTube as an example.
This does not happen during offline video playback.
My CPU and GPU usage are pretty high (50%) during playback.