For us to isolate your audio issue, it would be very helpful if you could answer the following questions.
Does the issue only occur on a specific channel or across other channels installed on your device?
Are you using an A/V receiver or soundbar with your TV setup? If so, what is the make/model of that unit?
In Settings > Audio > Audio mode, what setting do you have selected? Does the same issue occur if you change the setting to Stereo, etc.?
Moreover, if the issue only happens on one channel, removing the channel then adding it back in may help. Make sure to restart your Roku TV before re-installing the channel to ensure the process is successful.
He!lo...another user here has with the same problem. Its on multiple channels & has been happening for several weeks now. I've even selected the HDMI Auto detect when it was formerly set to PC master do but made no difference; no AV receiver or sound bar either.