On some Android devices, phone calls via softphone are played very quietly, the call quality is poor or you can hear your own echo.
We have worked out the following workaround to this issue:
It often helps to activate the connection service on the Android device.
The connection service is designated differently on different devices. For example, the setting for this can be found under "Call account" on some devices. Ultimately, it is a matter of registering ProCall as an app for telephony.
The problem is solved since Version 7.3.20.