I have 2 PMS with same agents/settings , one is on a windows VM, other is shieldtv.
Opensubtitles account is VIP.
Via VM : I can play movies with subtitles from opensubtitles agent; no problems.
Via shieldtv : I can see the subtitles downloaded by opensubtitles agent on the web GUI (web player), but if an external subtitle downloaded by opensubtitles agent is selected the transcoder will crash when lauching.
If an external subtitle not downloaded by opensubtitles agent is selected; no problems.
I saw this in the logs : ERROR - Couldn’t find the file to stream: /data/user/0/com.plexapp.mediaserver.smb/Plex Media Server/Media/localhost/3/[…]dd3bd.bundle/Contents/Subtitles/en/com.plexapp.agents.opensubtitles_[…]738da.srt
…
DEBUG - Streaming Resource: Terminated session … with reason Conversion failed. The transcoder exited due to an error.
Plex searches in /storage/…/Android/data/com.plexapp.mediaserver.smb/Plex Media Server/Media/localhost/c/…/Contents/Subtitles/fr/com.plexapp.agents.opensubtitles_e66…srt
But file dowloaded by opensubtitle is : /storage/…/Android/data/com.plexapp.mediaserver.smb/Plex Media Server/Media/localhost/c/…/Contents/Subtitle Contributions/com.plexapp.agents.opensubtitles/fr/e66…srt
This sounds exactly like a problem I’m having with my PMS on Shield TV. Getting the same Conversion failed error anytime it tries to play videos with Subtitles. Started within the last month or so and is driving me crazy. I’ve resorted to temporarily removing subtitles from all movies and turning off OpenSubs until it is fixed.
I hope Plex Devs sees this and can fix, it sounds like you may have found the problem.