Hi,
There is a known issue with the Raspberry Pi 3 where Bluetooth and WiFi interfere. My colleague @ab77 has provided details here: Build your own multi-room audio system Project - Sound is crackling or skipping - #10 by ab77
This is supposed to impact in case of balenaSound usage in multi-room setup with Pi3 as master server. Is Pi 3 the only device you have running or you have multiple devices running ? If you can have Pi4 be the master server here or an external BLE dongle with Pi3, we might be able to resolve this issue.
Regards,
Nitish