Amazon Prime Movie audio out of sync with video...here's why!
My problem was that the audio on Amazon Prime movies lagged behind the video by about 8-10 seconds. After much searching, I figured out what was causing the problem...It's not Amazon, but is a Roku caused problem that I have only experienced with Amazon Prime movies.
I have never used the ability to cast my iPhone photos to my TV via Roku. So I changed the device connect from "Disabled" to "Enable". Shortly thereafter my lagging audio problem began. I changed the option back to "Disable Device Connect" and the problem went away. I have gone back multiple times and enabled and disabled this option. Every time the option is Enabled, the problem comes back.
I'm posting this for others who might have the same issue. My solution is a work-around. I'm hoping that Roku can implement a real fix.