The game is playing at the moment, with the phone audio (non-call) sound setting set to minimum (which shows as an empty volume bar / muted icon), ergo the game has sound activated in its settings, but the phone has sound volume to 0.
A call is received.
A small, non-full screen pop-up is shown on screen to pick up the call, with the game still in the background.
You press the button to pick up the call. It goes in the background (ex, top menu bar). The game sound then plays at that moment that you start the call along with the speaking person’s volume.
I’ve only really reproduced it when taking a call, since when you are making a call the game is not in the background by default. I believe (not 100% sure) that minimizing the game later and returning doesn’t cause it to play the sounds again.
If I had to hazard a guess, when the call pop-up is dismissed to the background, the OS shifts the focus back to the game by default - as the previously opened window - while the phone call is handled in the background. That event, depending on how it is handled, might cause a mess with the audio settings.
Possibly I was unable to reproduce as on my phone (Pixel 4) when taking a call, the call screen completely fills the display. While the game is still running in the background, the call had overridden any game sound on my device.
Just to add I experienced this the other day. Also still on the older v0.37.
Device Samsung A20e
Steps to reproduce - exactly as @Norinth posted above.
I have the audio in game turned down to 0. Mid battle receive a phone call, small pop-up appears with the call buttons, answer it, but as well as hearing the person on the other end of the call I can hear the game music audio continue to play in the background - not as loud as the audio of the call, fairly quiet, but there when it shouldn’t be.
During the call I looked back at my phone and had to hide the game into the background and select the phone call, and that muted the game music.
Not sure if still there in 0.38 as I have now updated and not had another call mid game.