Run the check
Make a short local recording with speakers muted, then with them on low.
Check whether both app monitoring and operating-system monitoring are active.
Ask a call partner whether they hear their own voice or yours repeated.
Read the result
Echo disappearing when speakers are muted suggests acoustic leakage.
Limits and next step
The browser cannot inspect every remote call participant's audio path.
Repeat the check after changing one setting or connection. Keep a record of what changed before deciding whether the device needs service.