The hardware issue is the same as it was in the previous app, which was fixed in 3.68.1:
Plex for Smart TVs & TiVo - #72 by markus101 Maybe it’s not actually TV hardware related, but that seems like the most likely cause given secure connections add overhead.
When playing high bitrate content over a secure connection the device is unable to play the video without stuttering. We’ll be looking to make a similar change for this preview as we did in the public version to fix this.
It looks like the resolution of the app container is 720p instead of 1080p causing this, we have a fix coming for it to detect that case and scale accordingly.
In addition to a factory reset, we’re working on a fix to allow exiting without the need to factory reset.
Added to the list of known missing items.
This came up for Tizen users as well, I’ll add it to the known list while we work on a fix.