Previously been using this RX-V573 for a couple of years without issues. I moved it into a new room, and now I'm getting some annoying issues with the HDMI passthrough.When I have it set to HDMI1, which is my cablebox, it works fine. Switching it to HDMI2, which is the FireTV, I get horizontal distortions and the screen goes black every few seconds. 

Troubleshooting steps I've tried:
Multiple FireTVs and FireTV Sticks(all of which work properly when plugged directly into the TV)
Multiple HDMI cables with the FireTV
All of the HDMI inputs on the RX-V573
Multiple HDMI cables from the RX-V573 tothe TV
All of the HDMI inputs on the TV
Manually setting the resolution and refresh rate on the FireTV(tried 1080/60, 720p/60, and auto)

Firmware on all the FireTV/FireTV Sticks that I tried are up to date, as well as the firmware on the receiver. TV does not have updated firmware available.

Here's a link to a video I took to demonstrate what's going on. Only thing I haven't tried that I can think of is a different TV.

[youtube]https://www.youtube.com/watch?v=scZ4XKVBqzY[/youtube]

Damn that sucks, my firetv works fine with my old Yamaha receiver.  What I would recommend is jacking the firetv into one of your TV's inputs, and using your TV's optical out into your receiver for the sound.  Not as easy as simple passthrough but it works.  I only have a couple of HDMI inputs on my receiver so I have a five device auto switch and that's actually what my firetv is plugged directly into.  Might want to try that.

Very similar to what our blu-ray player is doing through our Yamaha receiver.  We replaced the bluray with a fire tv and it works great.

ETA: Ours is a different receiver.

I would try it on a different TV.

Which is what I did for the moment, and it works fine. But, this is for my parents place, so I was really hoping to make it more simple than that for them.