My Roku (Model 4660x Ultra) remote all of a sudden stopped controlling the volume. I now get a megaphone a circle Icon in top right of my TV when I press the volume but nothing else happens. The remote still turns the Sony TV on and off. Have repaired with TV, replaced batteries.
I had similar thing happen to my roku tv after searching IR codes for discrete channels, after the volume wouldn't work, instead of usual lone speaker Icon there was a complete speaker with tweeter and woofer. On roku TV's under Factory reset you have choice of resetting everything or just audio and picture settings, I reset the audio & picture and volume came back and lone speaker icon. I can see from 4670 ultra there is only resetting everything, I suggest you to do that. But that's up to you.