An update on my Plex situation. I was able to toggle the hardware acceleration setting off and back on, in the transcoder settings of Plex. Now I can start the movie i was having issues with at 20Mbps instead of the full quality and the DTS is transcoded into AC3, which is what is supposed to happen.
So transcoding is working correctly again. As far as direct play, it's a hit and miss issue, and it seems with everyone having different configurations here, ways of doing things, and even different media libraries, it could be hard to reproduce for someone else.
There are a couple things to note:
1, I use an Airport Extreme base station capable of MIMO beam forming 80211ac, which seems to have compatibility issues with ROKU (especially in the 5ghz spectrum) without manual configuration.
2. The Plex channel on ROKU seems to have issues with using all bandwidth available it seems.
my conclusions on this come from:
1. Not every high bitrate files fails to play in Plex via the Roku Channel
2. The files that have issues with Plex, and Roku, work with Plex, and other devices, or other streaming options on the same network without issues.
3. It doesn't matter if the ROKU is hard wired, or wireless, I tested that yesterday, and was able to produce the same issue either way.
So, at the end of the day, this looks like an issue to take to the Plex developers.
One other thing, I still see people stating that MKV is still not the more reliable format when dealing with streaming. It's gotten better, and for most of the times, it works just fine for me. Should I still consider putting my ripped copies of Blu-rays into a different format?