Could just be general power/grounding issues. It's present it all games?
All the gear is on the same outlet / power strip?
Is the sound present if you do things like turn off the tv, or unplug/power-off other stuff in the room?
You could power it up blind on an isolated power outlet and listen to at least confirm if the issue is external or internal in nature. (I don't have an AES but I assume it'll output sound even if it's not sending video anywhere)