You’re right.
My test was from macOS was with Plex Desktop and I definitely can reproduced it as often as i want 
So I think you’re on the right trail searching in this direction.
I already deactivated the enhanced video player on my ATV 4k - not a solution for me - as other users also replied 
Have you tested without the Enhanced Player any video that can be direct played? (no transcoding involved)
I wonder if it only happens when try to download a whole file regardless the player used, or if it works with the old player because it’s transcoding most of the time (meaning, it downloads the original video in small pieces).
Not sure. But I have disabled transcoding for some time to make sure that it’s not the problem. But I’m not sure if I have disabled the enhanced player in the same time.
I’ll give it a try tomorrow.
But I´m pretty sure that either the mac nor the ATV need to transcode anything with my tested movies
Yeah if it’s MKV, Apple’s video player can’t reproduce it directly. You would need an MP4 or MOV file file with compatible video and audio codecs (like h264 for audio and AAC for video).
Is there anything I can assist with or test on my end as well? I have the same setup of a Server 2019 Plex Server, and playing to Apple TV or any iOS device causes buffering.
I spun up a Server 2016 server, and it doesn’t have this issue, so, let me know if there is anything I can look at too. I really don’t want to have to rebuild a server right now, lol.
Since the last update of Plex for Mac (Version 1.8.0.1159-67c4a549) buffering disappeard for me… for now.
Wait&See if it is gone for all.
Any updates on this? I’m going to update to the latest beta of PMS to see if it fixes anything.
I’m having similar symptoms and I’ve been having them for at least one month if not for longer. This doesn’t seem to have anything to do with the Enhanced Video Player, at least not for me.
No matter what I do there are several h265/MKV movies that I simply cannot play on my Apple TV 4K using the latest Plex-app for tvOS. First I thought it was the 4K h265 causing issues, so I grabbed the same movies in 1080P h264/MKV but still the same issues.
Using the Plex-app they won’t start at all. Just endless buffering and nothing ever happens. Rebooting my server, my switches, my router, my Apple-TV etc but nothing helps.
Using Infuse Pro the movies will start to play but after 1 min - 2,5 min it stops dead and continuously buffers as well.
After reading through this thread I tried several things:
Server Version#: 1.19.2.2673
Player Version#: 2.16
Apple TV 4K tvOS#: 13.4
Server-OS: Windows Server 2019 (17763.1158)
I tried disabling various offloading options on my Intel X550 NIC on my Windows Server. Didn’t change a thing. I tried to switch NIC’s from the Intel X550 10Gbit to Intel i211 1Gbit and Realtek 1Gbit NIC but same behaviour.
Tried to disable IPv6 (I have a fully deployed native IPv6 in my home but Plex insists on using IPv4 regardless according to the dashboard but I decided to try disabling IPv6 on the Plex server just to test) but still the same.
I tried to switch from using Ethernet on the Apple TV over to using WiFi as my Ubiquiti Access Points are connected directly to the same switch as my Plex-server, whereas my Apple TV running Ethernet is connected to another switch. Less cabling, one less network switch just for testing. Same results.
Testing using the Plex-app on our PlayStation 4 Pro and Xbox One X and everything works on them. They are running Ethernet to the very same switch as the Apple TV.
Playback of the same movies on my iPad Pro and iPhone is also working. It’s even working when my server has to transcode from 4K HDR H265/HEVC. It’s only the Apple TV and tvOS having issues.
Decided to even try to factory default my Apple TV 4K, but still the same.
Best regards,
Thomas Andre aka RamGuy
EDIT:
Never mind. After 20 min playback on the Xbox One X it also stopped and just kept on buffering forever. It’s really hard for me trying to grasp what is going on.
Just chiming in today say we’re having similar issues:
LAN cabled all the way at gigabit.
EDIT: have turned off enhanced player on my wifes acccount (the one having the buffering issues!) and now the video is still direct playing but audio is being transcoded (DTS 5.1 -> AC3)
Will update if issue frequency changes with this change.
Any updates on this?
I just turned on enhanced player to see if the issue had been resolved on my ATV and it hasn’t.
Guess it’s time to migrate from Server 2019 to Server 2016
Migrated my PMS to a Server 2016. Haven’t had any issues for the past 3 days.
Can someone on the development team figure out why this is happening? You have plenty of willing users that can assist with grabbing logs and such…
I also switched - no time for the lazy developers.
Now my Plex is running in a docker container on my unraid-NAS. No problems either.
Honestly Plex need to set Windows Server 2019 to the list of “unsupported OS’s” - over a month after a lot of people telling them about the problem… disappointing.
Totally Agreed. Having to do a full downgrade on an OS is absurd.
Can we get a response from the devs? I had to reinstall windows server 2019 back to the February cumulative update to workaround the issue of the buffer constantly failing on Apple devices.
This is not a viable solution as I need to apply the latest Microsoft security patches. Is Windows Server 2019 supported or not?
Sorry, I missed this thread. I posted our findings about this issue in Enhanced Video Player on Apple TV 4K creating buffering issues - #61 by sergiou87
Right now we believe this is a bug on Windows side, but we’d like to get some clarification from Microsoft. Fow now, all we can suggest is to avoid using Windows Server 2019 to install your Plex Media Server, sorry 
thank you for the update. for me, it looks like the issue started after feb/mar cumulative update. i have reverted to backup and paused updates for now to see if there is any workaround for the server 2019 issue. otherwise, i will look to migrate to windows 10 as an long term solution.
Oh, did reverting the updates fix the problem? That’d be an interesting data point…
It did, playback returned to normal after I restored my VM. I also try installing May cumulative update with the same result and restored functionality by uninstalling the update putting me back to January patch level. I initially had this issue when I installed server 2019 for the first time but fixed it by disabling TCP offloading. The fix is still in place but something within the new cumulative update has broken the workaround.
