Server Version#: 1.20.2.3402 (Synology DSM 6.2.3)
Player Version#: 6.6 Build 11 (ROKU Ultra)
The ROKU PLEX Player appears in the Select Player list, but selecting it does not select it.
When using the ROKU directly it works fine, but casting from Windows is a no-go.
This also happened last November and the problem was in the ROKU PLEX channel app.
I think you are correct - they appear to be the same issue.
The way I use PLEX, this renders my system almost useless. This needs to be a priority fix.