Does the issue only occur on Amazon Prime Video or across other channels installed on your Roku device?
If you haven't tried yet, you can remove the affected channel and then re-install it. To ensure the process is successful, restart your device before adding the channel back in. We would recommend doing this from the Settings menu by navigating to Settings > System > Power (If you do not see a Power submenu, skip to the next step.) > System restart.
For detailed instructions, refer to this Support link: How do I resolve channel playback issues?
Let us know if there's any difference after.
All the best,
Roku Forum Moderator