Since it is affecting both these channels/apps, could be how the device is handling the video. Generally, it seems that whenever a device has issues with Netflix, it usually has an issue with Prime.
To troubleshoot, try lowering the resolution from within Roku. (Settings/Display Type). If you are using 4k, try lowering to 30mhz. Then try lowering to the HD resolutions (1080 and 720).
Can also try using a different HDMI cable as well as a different HDMI port on the TV. What is the model number of the TV you are connecting to?
Roku Community Streaming Expert
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Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941