Apple TV audio to Airport Express issue

I'm wondering if anyone has the same issue with a similar Apple TV 4 configuration.

I'm sending my Apple TV audio wirelessly to my Airport Express, which is connected to my stereo receiver where I can hear the TV audio on my stereo system. Meanwhile, the Apple TV video signal flows to my TV via HDMI, where I can watch the video. Everything works fine in this configuration.

However, when I Airplay anything from my iPad to the same Apple TV, the Apple TV audio resets itself from output to Airport Express to default HDMI output going to the TV. It's as if Apple TV can't handle 2 audio Airplay connections simulteneously, even though one is input and the other is output.

 

I think I tried Airplay 2 as well. My issue is really Airplay to Apple TV from iPad simultaneously with sending audio (Airplay?) from Apple TV to Airport Express. But will give it another go.. maybe missed something. Thanks for the suggestion.

 

Exactly put. I also understand Airplay 2 can send multiple audio streams simulteneously to compatible end devices. The question is if Apple TV 4 can simuteneously wirelessly receive and send audio. So far, it doesn't look so. I'm surprised there's very little documentation from Apple on this, at least from my efforts to find.