My TV is connected to a Pioneer AV receiver via HDMI and an optical cable. (Optical for when we plug stuff straight into the TV or watch Prime, etc and want surround) The TV keeps displaying "Setting up external speaker with Universal remote", then fails as no external speaker is connected. So I go into the settings, set the output to Optical (for the 300th time) and watch as it runs through the process again, setting the output back to speaker without me touching anything. So I set it back to optical and then it's fine. For a random time then it does it all again. Sometimes it'll do it a dozen times in an hour, sometimes it'll go for several hours without doing it.
I've disconnected everything, updated the firmware and done a factory reset. Still does it. Reconnected everything, still does it. Unplugged the optical cable and set it to speakers, still does it. Nothing I do stops this.