Asking this question here, that I also asked on Roku's forum, as it pertains to these TV, and I'm just not sure if it's the TV, the Roku App, the Roku itself, or what, and I'd like any help anyone can provide:
This problem is bugging the heck out of me. Everything has been fine for a couple of days since I got the thing, but now, for seemingly no reason (I've changed nothing since the initial set up of the TV, and before anyone asks, the settings are on on my TV to enable 4K HDR 60 on the supported HDMI ports, it's a Sony X900E. I know that's the problem people always suggest first. It's not that!) The problem is this: When I first set everything up, 1080p 60 on youtube worked fine. 4K 60? Also fine. 4K 60 HDR? Fine too!
Come yesterday (and still now), not so. 1080p 60 works... on some 1080p/60 youtube videos (but not all), 4K 60 videos are playing back in 4K at 30 FPS. Likewise with 4K 60 HDR. (The HDR works, though!).
This is only with youtube, too, on the Stick. I don't know a way to test 4K 60 HDR on it outside of youtube, but 4K 60 works on Plex just fine, and every other app is doing what it's supposed to be doing normally. It's just youtube. (I've also ran every speed test I can possibly run. I've got pretty fast internet (300Mb down/50 Up), and the wifi connection to the Roku seems ultra-stable by all metrics I have that I can test it. Other wifi devices are fine. I'm able to consistently get 4K/60 on the TV's built in youtube app (it can't do HDR, though) and I'm also able to consistently get 1080p/60 on my PS4. Is this normal? Is it a Youtube problem? is it a problem with the stick?
Oh, also, some youtube HDR videos have a slight... I guess flicker? Every few seconds, for like a milisecond, the screen will flash black. Doesn't happen with all HDR videos, but it happens with a good few. (For example, if you find the HDR LG test video of like.. chess or something? It's one of the videos on the HDR channel on youtube). Is that normal? It only happens with youtube. Nothing else.
Edit: Here's a video of a video that should be 60 fps, as well as flickering with HDR:
My video: https://www.youtube.com/watch?v=EyqUqslBiD0
Original video I'm watching in the clip: https://www.youtube.com/watch?v=2RIDhA9c8qw