[maqer]

My LG 65UF8500 used to play 4k videos through the youtube app without an issue. Now anything maxes out at 1080p, even previous subscribed 4k videos won't reach max resolution anymore. Deleted the app, restarted the tv, no fix yet. Anyone else have any issues or tips? Other apps such as amazon prime plays UHD videos just fine. Seems to only be limited to youtube. Appreciate any help .

[Poilaucul]

I have the same issue, this is due to the Youtube app detecting your bandwidth during a very short period of time at the startup of playback, and adjusting that resolution to your bandwidth for smooth playback without buffering.
The problem with this is that if you don't care about a little buffering at the beginning you're stuck with video at 1080p instead of the 4K you would prefer over bufferless video playback.
What youtube must do is let the users choose it override this behavior by introducing a "always load best quality available regardless of my bandwidth" option.
To have a shot at getting this feature you must submit a comment to https://www.youtube.com/tv_feedback
The more we will be to request it the most chances we get.