The classic configuration is all sources are run to the receiver then video passes on to the HDTV. ARC as you know (or maybe not) is not always reliable. We tend to set up like this:
All sources to the receiver passing video to the HDTV. Then if ARC works, that's for HDTV antenna and app play.
Your setup is likely to just have issues that Sony or others can't fix.
So I just got a Sony X900E tv a couple days ago. My amp isnt 4K, but it has ARC capabilities. I have my satellite receivers and my android media box (beelink g1 ultimate) plugged directly into tv, then hdmi from tv to denon avr 1911 amp for ARC audio. If I use the android box, then turn it off, and switch to another source (bell expressvu as an example), I lose ALL audio abilities with my amp. The only time it works is if I keep the android box on or in sleep mode. (also if I press the input in the sony remote to switch ports, at the top of the list is the media player it says PLAYER 1, then the box name, and HDMI 4 (the hookup Im using). Not sure why it says Player 1 and is seperate from the list of other systems (but also has the option of selecting HDMI 4 further in the list as well). Any thoughts?