Hey guys.
Before Christmas break, I was watching HDR files, no problem. They would play nearly instantaneously on the Apple TV 4K, and could play on the PC as well (although my monitors don’t have HDR so it doesn’t really work properly.)
When I came back from holidays in the new year, HDR files will no longer play on the Apple TV.
To my knowledge nothing has changed since before Christmas on the Apple TV side (I think it doesn’t update the Plex app automatically), but I assume I’ve probably gotten at least one or two server updates since then. (December 22nd through January 2nd)
Doing some testing, a random HDR movie takes 40 seconds to several minutes to load up on the PC (which doesn’t support HDR, but always started playback pretty much instantly in the past), the Plex Transcoder process hits ~50% CPU usage, but the movie just stutters completely and uselessly, giving me a few frames of playback every 10-15 seconds.
Meanwhile, the Apple TV Plex app just won’t play the file at all. It just tries for about 20 seconds, and then gives a “Couldn’t retrieve the play queue for this item” error. So it appears to be a poorly explained time-out error message.
This was not an issue before Christmas, and aside from random files in my collection, I am testing the exact same file I watched flawlessly mid-december, and now it won’t play. Am completely stumped. 
Now these could be two separate problems, or the same one, but they happened at the same time so I’m assuming this is linked:
In the Plex player (Apple TV one, or PC browser ones), when I just go into a HDR movie (before I hit the Play button), the Plex Media Server process jumps to ~17-30% CPU usage, and doesn’t drop down again for roughly 30-100 seconds.
Go out of the movie and right back into it (again, without hitting play), we’re up to ~40-55% CPU.
Third time, 50-60%, fourth time, 60-80%, fifth time, 85-90%, with CPU maxed out because the rest of the operating system needs something too… 
Apple TV connected via gigabyte LAN with WiFi disabled.
PC playback is actual Plex Server machine.
Have rebooted everything and tried to update everything. The only thing that wanted to update was the tvOS, from 15.8 to 16.2 but that made no difference.
Log file folder has ~70 logs in there, and I have no idea which one you’re interested in, but happy to attach one if you tell me which is the tasty one and where to put it. 
Server Version#: 1.30.0.6486 (32 bit version?)
app.plex.tv Player Version#: 4.98.2
localhost Player Version#: 4.87.2
Apple TV Plex Version#: 8.6 (3177)
Apple tvOS Version#: 15.8 & 16.2
