Server Version#: 1.13.6.5339
Player Version#: Web 3.63.1
I upgraded to Plex Media Server 1.13.6.5339 from 1.13.4.xx on my Synology 1815+ running DSM 6.2 yesterday. (I had skipped the 1.13.5.x builds because when I applied them, the new network selection code selected the wrong interface and took Plex offline. 1.13.6 fixed this for me.)
The server started fine, but now when I try to play back any video content, either using the web interface or the Win10 app, I get a “Conversion failed. The transcoder exited due to an error.” error. I enabled debugging and restarted both the Plex Media Server package and then the NAS itself, and in both cases I still get the error as soon as I try to start any video.
Chuck suggested disabling IPv6 from the Networking settings on the server, and after doing so and restarting the Media Server package, that solved it for me.