pHat BEAT loses ability to play audio from Docker container

I’m running using the pHat BEAT with MPV from a Docker container using Balena.

I’m running into an issue where there is sometimes no sound output. MPV is definitely playing (or at least the playback position is increasing), but there is nothing coming out of the speaker. Power-cycling the Pi seems to fix it.
I’ve noticed it most frequently when a new version of the docker container has been pulled, but the pi itself has not rebooted. It’s possible that other times are where the container has crashed and restarted.

Do you have any idea why this is happening and/or suggestions where I could look in order to troubleshoot?

Thanks in advance