My server version is 1.14.0.5470 and I have no problems with buffering on any of my Plex clients, which include the same devices as you have mentioned. There must be some sort of configuration issue or it is something external to Plex, despite the fault finding you have already attempted.
@Krazeh I would have agreed with you but the problem is far too widespread, and those of us who have spent countless hours working on this can reproduce the issues by downgrading two versions and then upgrading again.
Not to mention, the issue does not appear on Linux server version (Well not widely reported) and or QNAP server installs, which bot run different versions to the windows server edition.
And the problem does not show up straight away, it can take a few days, sometimes a bit longer before it starts to happen, the issue is not immediate as discovered from fresh install testing.
Also configuration should not be an issue as the configuration is copied and used in fresh installs to ensure consistency between versions in testing.
I truly hope that you do not get hit with the problem, but if you do, please report it 
Cheers,
David.
Well figured I would provide an update, I manually updated the server to the latest version as listed on the website, since the automatic update would not see a new version.
Version 1.14.1.5488
At first it seemed to work reasonably well but then the buffering issue raised its ugly head, but this time, it is worse than before in that video now artifacts quite substantially before it begins to buffer.
I cannot find the fundamental issue between the versions where this problem was introduced, I am pretty well stuffed as to what is causing the issues as there appears to be multiple different reasons.
I am going to rebuild the server on an entirely different machine now and see if that improves the situation.
Any update from Plex support when this will be fix ?
Its clearly not an issue with the hardware hosting the plex server app.
This ongoing LG Plex buffering problem seems very sad. I’m regretting buying the LG. The main reason I got it was price and Plex compatibility. Next time sticking with the Samsung. Don’t have buffering problems with the Samsung. Both are connected to Gigabit LAN even though both have 100MB ethernet. Why they haven’t just supplied them with 1GB ethernet in today’s day and age I’ll never know. Anyway, I hope there is a solution to this buffering problem
Wow!! Works!!! After 2 days of pain. Thank you man!
Glad it helped! 
Thx for the feedback!
Hello everyone. I bought a new LG B8 a week ago, have the same problem with the Plex app as many people in this thread. Some 4K Hdr-movies buffers/lags every now and then. Exact same problem in the Xplay app. It´s pretty inconsistent too. Some 4k files work great and other get chopped up all the time.
1080p and TV-shows work great (I watched Planet Earth II in 4k HDR, no problems there).
My server is set to “nearby” ni the app with the green lock lit and it uses direct stream.
Hi,
I have the same problems described here with the buffering. Sometimes it plays well and sometimes not. And sometimes stops at 2-3 seconds for many time, unaplayable.
In the other hand, the WiFi is on normal channels and have 200Mbps bandwidth, so the problem it’s not there.
I have configured (Plex and Xplay, booth have the same problems) with direct stream, no transcoding, and even that way, sometimes the computer starts to do the task of transcoding.
Last, this is the worst, some files shows correctly in description as H265 HDR 4K, but starts the streaming and the TV dosn’t switch to HDR mode. If i take the file, and duplicate it on another directory, problem solved. Nonsense.
I have also a Nvidia Shield. If i try to play the same file on the same network on Kodi or Plex on Nvidia Shield, everything works perfectly.
So… what’s going on with LG and WebOS?
I had given up and purchased an Amazon Fire TV. No buffering ever.
Yesterday I forced the LG Plex client to use insecure connections on local network and most of my buffering issues are gone. It still buffers some, but only a few times during the movie. I gave up trying to get 4k movies to play. I just copy the 4k movies to a hard drive and plug it into the TV. Not optimal for the entire house, but I ran out of patience with 4k and Plex.
Just bought a OLED55C8 (2day before CES2019… 
) and done some test.
Test environment:
Plex server (Version 1.14.1.5488) : DS918+
Lan: 1G cat6 lan
Test video: Jellyfish Video Bitrate Test Files (all no sound track, video only)
jellyfish-60-mbps-hd-hevc-10bit (usb play ok , plex play ok)
jellyfish-90-mbps-hd-hevc-10bit (usb play ok , plex play ok)
jellyfish-120-mbps-4k-uhd-hevc-10bit (usb play ok , plex play buffer)
over 120 mbps all will buffer.
Still wonder why LG use 100lan these day on flag ship TV… 
4k HDR TrueHD file which confirmed TrueHD not support by C8 so plex will trans code and buffer.
So at last , the C8 can direct play 4k HDR without buffer if :
- 4k HDR bandwidth below 60mbps
- DTS sound track (from my 1080p)
- can use srt subtitle (I only have srt anyway)
Personal advise, try wait everything for new generation if no urgent need because of HDMI 2.1(much bandwidth upgrade) is out and many things will change ! 
Good luck all !
Tested plex player on my phone and laptop with direct play and everything went smooth. On my LG B7, intermittent playback, buffering all the time. Waiting for a fix. : (
I recently bought a LG OLED65C8 which has the Plex player app installed on the TV. When I tried to play 4K video via WiFi streaming to Plex there was constant buffering. What I figured out is that my WiFi router was configured to provide both a 2.4 and 5 GHz WiFi network using the same SSID. While this configuration works fine for my iPhone and Macs, I discovered that the TV was constantly joining the 2.4GHz network instead of the 5GHz. The solution was to change the SSID of the 5GHz network to differ from the 2.4 and join the TV to the 5 network. All my buffering issues went away after that.
Hummmm… that is interesting. Recently I changed my internet contract and they installed a 2.4/5Ghz wifi router to provide faster internet connection. My PC (server) is connected via 2.4ghz (I’ve just bought a new dual band board that I have to install), and the rest (phone, laptop, TV) on the 5ghz. That may be the problem, but I’ve already tested plex player with my laptop on the 2.4 and 5ghz network with no buffering. With the TV settings opened it doesn’t seem to be changing networks, though and it buffers on both 5ghz and 2.4… I’ll test it and come back with the results.
Ok, using the latest Plex Server on my pc, webOS 4.1 on my LG tv, latest plex app for lg.
Connection is wired.
Buffering, like the rest of you.
I’ve tried most of the stuff written here. Disabled secure connections. Allow fallback to insecure connections - on the same network. Media server status is nearby and doesnt have green lock. Turning off Dorect Streaming.
…aaand still buffering.
One thing I dont know how to change:
On my PMS , when Now Playing on TV, it says “Transcoding from HEVC to H264”
As I gadered here, it should say “Direct play” or something like that?
On my client, preferred settings for all content is “original”
This is my update:
New wi-fi board with 5Ghz connection like the TV (450Mbps). (Had tested before with both on 2.4Ghz also)
Killed my 2.4Ghz connection in the modem configuration. They already had different wi-fi names (SSIDs).
Still buffering. : (
Sorry to hear that. The only other thing I can suggest is doing some type of WiFi scan to see if there are any other WiFi networks in the 5GHz range that are using the same channel as your setup. On Macs the wifi diagnostic utility has such a scanner which I use regularly to pick my WiFi channels.
This internet company router has something similar, but i don’t think the channel is the problem, as i was not experiencing buffering before, including with all equipment on 2.4Ghz, which also gives me buffering now. Keep in mind that in my laptop or cellphone there is no buffering at all with plex player.
Just tested with the best signal channel, witch doesn’t have any competing connections in the area. Buffering…
Flash drive it is.
update:
tried LG’s Smart Share and their Media Link (somewhat plex) I found in this link: https://www.lg.com/br/suporte/smart-share
no success. Where is LG on this issue?
Alternate solution:
Go to your screen share app and turn “listening mode” off. This increased my wi-fi speed a a lot. But, i still get buffering on higher bit rate files (20mbps)
Changing wi-fi channels did nothing for me…
Thank this guy: https://www.cnet.com/forums/post/f85555a2-7f10-427a-af5d-94cfbc5a38d2/
some other advice: https://www.avforums.com/threads/lg-b7-oled-tv-owners-and-discussion-thread.2094250/page-206#post-26842722
I think this was affecting my other wifi dependable apps quality also (like Netflix that would not stream in 4k). Try this: access fast.com on the TV browser before and after turning “listening mode” off to see how the wifi speed changes.
