I have experienced this exact problem for a very long time. I believe the first time I experienced it was during the ROKU updates in the 9 versions. Over the years, I have purchased an Amazon Firestick, ONN 4K stick, an android based TV, and a ROKU-based TV. I have only experienced the issue on ROKU products. I have been in touch with ROKU support multiple times and was given the 'it is a DirecTV stream problem." After multiple calls back and forth, hearing the same corporate line, I decided to purchase a ROKU Streambar with a 2022 build date. This means the latest hardware and software. The sound issue has gone away with this unit. My old ROKU products, including the ROKU-based TV, STILL have the issue.
If this problem bothers you as much as it bothered me, you can either buy a competing product or buy ROKU's latest offering.
Good luck.