Auto-ducking (dropping volume) out of control

Auto ducking is out of control--volume suddenly drops without my touching the volume setting--I have to reboot apps or the device to get back to normal volumes for the volume setting, for weeks or a month now. It happens with different video or podcast apps, iPad & iPhone (iOS 18.2.1), device speakers or airpods.

Nothing is set to be 'listening' or 'speaking': Siri is not enabled, Maps is closed.

I am sure of at least 2 distinct triggers:

One is the Stelo app, when I inadvertently tilt the device from portrait to landscape mode with Stelo open to the glucose graphic screen. (I have not given Stelo permission to give me any notifications so there is zero sound output expected from it; Stelo is not loaded on iPad, so it's not only Stelo's fault).

Another is outside noises, like dishwasher starting up.

What can I do to prevent this?