Hi Random1
Thanks for the post.
Starting Roku OS 10.5, we added a new Power item in Settings > System menu for some Roku models. If you have this Power item, under Auto power savings, see if deactivating after 20 minutes of no interaction fixes the problem.
If the issue persists, please be advised that some streaming channels employ their own mechanism to cease data usage after a specific period of inactivity. These features will not be affected when you disable Bandwidth Saver.
I hope this helps!
All the best,
Kariza