macOS Big Sur iTunes playback with lid closed and controlled by iTunes "Remote" app

Hi there, first time posting to PC-Audio here. For years on my MacBook Air if I had iTunes open and the lid closed, I could start music from the iTunes Remote App on my iPhone and it would play through my USB DAC. I was last using Catalina. Yesterday I updated to Big Sur 11.2.3 and now it is not working correctly. I can see the iTunes (Music) library from the Remote app, I can open it, I can play a track, but after 15-20 seconds it stops playing. If I start it again, same thing a few seconds and then stops. If I leave the lid open just enough to for the laptop to stay "awake" there is no issue. But I am unable to get it to play continuously with the lid closed like I used to. Even though I can "wake" the machine from the app, see the library, pick and song, and play it, it will still stop after less than 30 seconds.

Anybody have some advice about this? Thanks!
Andy