[bug][Jolla C?] Android layer does not release audio pipeline (sometimes)

Sometimes I can hear some sort of low noise from the loudspeaker, even if no App is running. When this happens you can not change the ringtone volume with the volume rocker, but instead control the playback volume with it (which does not change the volume of the noise, nor is there any app that could be controlled). The only way to get rid of it, is to stop (and restart) the Android compatibility layer or reboot the device. After that the noise is gone and the volume rocker controls the ringtone volume correctly. I didn't check the impact on the battery, but I think this bug causes some battery drainage because the loudspeaker makes the noise permanently.