Same issue here - here are responses to requested support info:
-Device model: 9102R Streambar
-Serial number: YLOOAKO85305
-Device ID: 2A109AO85305
-Software OS/version: 10.0.0 build 4192-95
-Does this issue occur on a specific channel? No, I have sampled and duplicated the issue on several of my Roku channels, including content on The ROKU CHANNEL.
-Tracker ID: 05-186-672
-Issue and Steps to Reproduce: Issue is the on-screen Volume level icon (indicator) popping up, even when volume level is NOT being changed. Occurs during or toward the end of the short buffering period when video starts playing; also when using the "BACK" button to leave currently playing video. And while the issue still involves "video", it happens during the inserted "ad break" initiation and begins again when the ad break ends, returning to video of desired program.
-Image of the issue - I actually have 2 videos at the following YouTube links. They show volume icon appearing at video start and when I used the Roku remote's BACK button to exit the same video:
Video 1: https://youtu.be/VP5ABjwXkuo
Video 2: https://youtu.be/oxn6FlayWaA