Is your HDHR Flex able to see the 7.1 channel via the scan (check in the Flex’s web interface → channel lineup), or is it just Plex not able to see it? The Plex channel lineup is separate from the HDHR channel lineup, but it would be interesting to know if the HDHR can see that channel.
Also, please turn on debug level logging on your Plex server. Error level logs don’t provide enough information to troubleshoot. Log snippets can also be a challenge, so the best chance for problem resolution would be to upload full debug level logs covering an example of the problem occurring.
