Thanks for the inquiry.
Is Amazon Prime Video the only channel that you are experiencing this issue with? If so, that is likely an indication that the issue lies within that particular channel. In these cases, the channel provider will need to investigate the issue in order to help resolve it. I'd recommend reaching out to Amazon Prime Video directly to report the issue and request additional support. Many channels on the Roku platform are developed and maintained by the channel provider directly, and they'll be able to best assist.
You can reach them here: https://www.amazon.com/gp/help/customer/display.html?nodeId=G9SY6AQJV45JFMET
Roku Community Moderator