Sonar needs the music stream to emit ultrasonic signal and we need to keep sonar volume at maximum to maintain reliable results.
Unfortunately, this also affects media volume in 3rd party apps as we cannot control those separately from sonar media volume. This means that while using sonar, you can only use media apps on full volume.
We have also added a separate volume settings for lullabies, you need to set your lullaby volume upfront and let the music volume maintained by the sonar.
When using sonar, you cannot control lullaby volume by volume buttons as it always jumps back to maximum.