Airplay settings reset after sleep

I recently updated my old 3rd gen Apple TV with a 4K model. In my setup, I have the apple tv hardwired into my network, and I airplay the audio from the apple tv to an airport express that my stereo is plugged into. On my old 3rd gen, the airplay setting was a "set it and forget it" type deal. I would set the audio to output to the airplay speakers in the audio settings, and every time I used the device, it would play the audio through the airplay speakers. Reasonable enough.

Now, whenever I wake the 4k from sleep, the airplay settings are reset to playing directly through the HDMI (which in my case is going to a projector on my ceiling with a tinny mono speaker.... not ideal). I am having to change the setting back to play audio through my airplay speakers every time I turn on the device. Its very annoying, especially considering my old device handled this so well.

I read on a forum that you can fix this problem by assigning the apple tv a static IP address on your router, and manually entering network settings on the Apple TV. I tried this, but it didn't fix the problem at all. Is there anything else I can try, or is this just another case of Apple's slipping standards when it comes to user experience?