I have an UN55NU8000FXZA TV and it's driving me nuts. I have a sound bar connected via Optical and set the audio out to Optical. It works fine until the sound bar is powered off and back on. The TV switches the default audio back to the internal speakers and doesn't recognize the sound bar until I go back into the menu and set the option. It should remember this setting! The sound bar needs to be turned off when I connect my BT headset so nobody else is disturbed by the sound. No TV I've ever had changes the default audio back on its own, this is specific to Samsung.
I can't use HDMI for this, has to be optical. All of the normal culprit settings have been checked, the smart features like anynet and all that are on, this is frustrating.