After reading reviews here to confirm that these cables are 4K HDR10 capable, I ordered a set of three to run in the wall between various devices and a new LG 4K tv. They work fine with regular HD devices, but connected to an Xbox watching 4K Netflix, they fail within a few seconds every time. It'll show a few seconds of the video, flicker to static for a second, or show noise patterns, then go blank. Switching back to the HDMI cable that came with the Xbox works flawlessly. All three cables exhibit this problem, so this doesn't seem to be a one-off issue.
The Xbox renders all its menus and other output at 4K all the time, but the only time the cables fail is when Netflix enables HDR10 (the tv shows a little HDR badge in the corner when this happens), so I'm assuming the incompatibility is with HDR10.