Audio not syncing

I had to spend a few days testing a theory and it turned out to be the cause of the issue. It's actually something that possibly affects all AppleTVs.

The top of my Denon receiver gets pretty hot. It's uncomfortable to touch, possibly around 120 degrees F. I had the new AppleTV box sitting on top of the receiver, not thinking about how the heat might affect it. Realizing this might be an issue, I moved the AppleTV box to the side of the receiver. A short time later the audio syncing started working perfectly.

So I thought it was worth another test. I took a different AppleTV box (it's a 4K model I use in another room, but not the latest gen) and placed it on top of the Denon and left it there for a few days. After about 2 days it also started developing the same audio sync issues.

I suspect that the fine tolerances on modern chip components are exceptionally sensitive to heat, as it can expand metal elements just enough to cause problems like these. Add to that the closed environment of the AppleTV and the compact nature of the unit itself, and you have a perfect environment for this kind of problem.