I specifically get this error only if secure connections is enabled required at the server (not Preferred), and only when playing DTS or TrueHD codecs.
If I disable secure connections and allow insecure connections, it then transcodes the DTS and TrueHD codecs for my Samsung TV again.
I report this issue on this thread at well: Plex on Samsung and LG Smart TV become slow and lagging interface - #20 by MarPlex
And tagged @sLumpy which seems to be a Plex Employee aware of these issues with Samsung and LG TVs
