I have the same issue. Roku Express 4k+. Have it connected via HDMI direct to tv. I've tried removing and adding the app. Changing cables. Nothing helps. Always drops sound several times during movies.
Can you please provide us with more specific information about the issue you are experiencing? What is the affected channel? If the issue only happens in a specific movie, would you mind providing us with the title of the movie?
Did you restart your Roku before re-installing the channel? That step is crucial when performing the troubleshooting. If you haven't tried the suggested order (remove > restart > re-install).