How do I get plex to play non "standard" video formats?

I recently updated my server OS I went from Ubuntu 14.04 to 16.04. The upgrade went through without errors all my settings seemed to stay the same, but now certain files on my server will not play I get an error “Conversion failed. The transcoder crashed or failed to start up.” This error always occurs when I attempt to play a video that is encoded with VP8. Plex played these videos fine before the system update, now it does not. What am I missing? I have tried reinstalling plex, I have tried reinstalling codecs and am unsure what else to try to get this going again. Any assistance you can provide would be greatly appreciated.

What do your logs say? Have a look in [plex_root]/Library/Application\ Support/Plex\ Media\ Server/Logs/ and then especially in the “Plex Media Server.log”.

Here is a paste of the log
https://pastebin.com/wCz0eyZC

I can see that it failed but am not able to parse the reason from it.

with a big stick beat it until it know who is boss

Can anyone help me figure this out?

@Quantafac said:
I recently updated my server OS I went from Ubuntu 14.04 to 16.04. The upgrade went through without errors all my settings seemed to stay the same, but now certain files on my server will not play I get an error “Conversion failed. The transcoder crashed or failed to start up.” This error always occurs when I attempt to play a video that is encoded with VP8. Plex played these videos fine before the system update, now it does not. What am I missing? I have tried reinstalling plex, I have tried reinstalling codecs and am unsure what else to try to get this going again. Any assistance you can provide would be greatly appreciated.

A lot of recent failures to convert (for me anyway) were related to crappy subtitles. Force refresh the metadata on the item in question and it may clear it up. Just disabling subtitles works fine, but replacing them fixes the bug completely.

Unfortunately that made no change. I usually do not run with subtitles and am unsure how I would replace them anyway as they are within the video container (.mkv). I attempted refreshing the metadata and it did not work. The way I have these videos encoded are VP8/OPUS/MKV, I prefer using fully open formats for my videos. It worked before the system upgrade so I am thinking there is a random backend application that broke, but I am unsure how to determine where it is breaking. I have tried upgrading and downgrading plex with no change.

Can you restart PMS, wait 3 minutes, recreate the problem, then provide the entire log package from Plex Web.

Sorry it took so long to get these to you, here are the logs.

Have you been able to find anything in the logs that can help?