Welcome to the Roku Community, @TimTheMadDog!
Thanks for reaching out. We'd like to share some steps to help you resolve this.
If your device has been streaming for four hours without receiving commands from your Roku remote or the mobile app, the Roku platform interprets this as inactivity on your Roku device. If you do nothing, playback will stop after a moment, your Roku device will exit the channel back to your Home screen, and data will no longer be downloaded over your internet connection.
To disable this, you may navigate to your Home screen. Scroll up to down to select Settings > Network > Bandwidth saver > Off.
For reference, you may visit our support article dedicated to this: How to use Bandwidth Saver to avoid going over your internet data cap
Please keep us posted on how it goes and we'll go from there.
Best regards,
Carly
Carly Y.
Roku Community Moderator