This looks like the failure seen on Windows that started to be encountered from last September / October
Mar 14, 2019 12:54:09.471 [3724] ERROR - [Transcoder] [stream_segment,ssegment @ 03141480] Failed to open segment list 'http://127.0.0.1:32400/video/:/transcode/session/3a0bc154-3003-440e-932b-c9d32680a430/7f186c26-1124-48fa-b3be-9d12e500837c/seglist'
Mar 14, 2019 12:54:09.479 [1976] ERROR - [Transcoder] av_interleaved_write_frame(): Unknown error
Mar 14, 2019 12:54:09.481 [2820] ERROR - [Transcoder] Error writing trailer of media-%05d.ts: Invalid argument
Mar 14, 2019 12:54:09.505 [1928] DEBUG - Jobs: 'C:\Program Files (x86)\Plex\Plex Media Server\Plex Transcoder.exe' exit code for process 3288 is 1 (failure)
The unique identification of this is it always has this error logged ERROR - [Transcoder] av_interleaved_write_frame(): Unknown error coupled with failure to open a segment list or manifest through localhost eg ] Failed to open segment list 'http://127.0.0.1:32400/video/:/transcode/session/3a0bc154-3003-440e-932b-c9d32680a430/7f186c26-1124-48fa-b3be-9d12e500837c/seglist'
This first impacted users after a windows update identified as the Windows 10 July 10th 2018 update. Microsoft fixed it soon after with a 16th July 2018 update
The problem came back in October or so and until recently the cause was not identified. Recent investigation bt user @XenonMB in this forum topic identified the cause as MalwareBytes Web Protection which must have changed to coincide with all these issues
Start reading posts by @XenonMB from this post onwards
Join the other thread and if you are using MalwareBytes Web Protection try to reconfigure and report the outcome there
