We have a 1 year old ROKU Ultra. Starting today (June 29) the volume on the Samsung television conntcted to it spontaneously lowers to zero (0). At times, no volume indicator appears when I pust the volumn button. At other times it appears, the volumn starts to increase but then "dives." Still other times, it will work normally for a few minutes and then go down to 0. The other day there was a significant audio/video sync issue but it resolved itself.
I have rebooted the TV and the ROKU; switched the batteries, disconnected all cable and power and reset the Roku box. I can find no support for this issue on the Internet.