Losing signal to Onkyo AV and TV
REF: https://discussions.apple.com/thread/252115751
I have finally found a solution to this issue, just in case others are grappling with the same problem.
Solution:
Get the ultra-high throughput 4K certified Belkin cables (cable IN and cable OUT).
Both HDMI cables from the AppleTV into the Onkyo AV and the able out to the TV must be the Belkin 4K certified.
AMZN sells it as well.
Signal is now steady and stable.