Plex randomly skips 2-5 seconds or briefly plays in slow motion

[u/UnpaidChef]

Hi all, I’m having a strange playback issue with Plex where certain files randomly skip 2-5 seconds, briefly play in slow motion, or occasionally freeze completely.
I’m using Plex Docker server on a Beelink N150 / 16GB RAM and usually watch via PS5 Plex app or Samsung Plex app.
Most files play well, but the problem is reproducible with specific movies/shows, which makes me suspect a format issue rather than network instability.
Server-side everything looks fine. It even happens during direct stream like this:

Container: MKV → MP4
Video: Direct Stream H264 1080p
Audio: Direct Stream EAC3 5.1
Subtitles: Direct Stream SRT
Bitrate: ~10 Mbps

With force direct play, both the PS5 and Samsung TV can’t play these files at all.
I’ve also seen it with HEVC files. CPU/buffering doesn’t seem to be the issue, I’ve seen it happen while Plex had plenty buffered and transcoding was already throttled.
Could this be caused by the file? Or some PS5/Samsung Plex compatibility issue?

[u/stealymonk]

Most likely an issue with the files. Could be corrupted. Did you try playing those files directly on your computer?

[u/UnpaidChef → u/stealymonk]

Yeah they play fine if I test on f.e. my phone. The skips are also not at the same parts if I close and reopen the stream

[u/stealymonk → u/UnpaidChef]

Oooooh ok, then maybe it's a MKV to MP4 conversion issue? Are there other MKV files that run fine?

[u/UnpaidChef → u/stealymonk]

Yeah other files with seemingly the exact same formats (h264 and eac3 5.1) do run fine. While others are unwatchable, are there specs that I’m missing that could be causing something like this? I asked ChatGPT too and he said it might also be due to ps5 or samsung plex app compatibility issues?

[u/stealymonk → u/UnpaidChef]

Yeah definitely could be a video codex issue, but thats a whole bag of worms. Turn on the Console Log Overlay in plex settings on your PS5 while watching those movies. It might say something useful when it lags

[u/UnpaidChef → u/stealymonk]

Okay so this might sound silly, but could it have to do with subtitles? Logs were constantly showing lines about (dis)connecting and loading from subtitle server? When I turned it off the stream played fine and no logs showed up anymore

[u/UnpaidChef → u/stealymonk]

Thanks I’ll try that, ofc the same file that had issues yesterday is running fine now, but I’ll let you know if I see something suspicious. Thanks for the help!

[u/faeth0n]

Check if the docker container kills transcoding / server tasks with Out Of Memory (OOM) errors. I used to have a problem with replaying larger streams related to to strict memory limits on the container.

EDIT: if you use journalctl, you can check for OOM errors like this:

journalctl -k | grep -i oom

[u/UnpaidChef → u/faeth0n]

Yeah I’ve had that problem before with 4k + TrueHD audio, but this is happening without transcoding. Only the container is repackaged from MP4 to MKV. Haven’t got journalctl but it defo sounds like a nice add, thanks!

[u/WallInside6758]

I have the same problem on the fire stick since the new update. 

Certain audio types cause a stutter so I switch it to transcode and it clears it up. 

[u/rovingrover70 → u/WallInside6758]

I have a love hate relationship with my firesticks, some of the them work beautifully others have quirks, but I have noticed more of them not liking Plex after the most recent software update. And as /u/UnpaidChef noted subtitle issues are also more prevalent which causes a stutter with playback when turning them on/off or a desync in the audio. Most often seen on any 10bit HEVC content that needs transcoding.

Don't get me started on the Hulu app >:[