I assume that if you turn off the sat box the audio drops as well? If so that is one fix, but obviously you have able through somewhere. I think your best approach is start unplugging the HDMI and/or audio connectors one by one till the sound stops. Then try a different cable on that connection. You mention having HDMI 1 connected direct from SAT out to TV in, do you also have a SAT out to the AV7005 and the a HDMI from the Av7005 to the TV? If so why the direct SAT to TV If the TV speakers are turned off?
Netflix and Marantz AV7005
I have a Samsung smart tv hooked up to my Marantz AV 7005 pre-amp. When I select Netflix on the tv ,the netflix comes up with audio, but audio from the previous satellite channel also plays in the background. I have the hdmi1 arc out connected to my set top box in on the Samsung TV.