SFOS 18.104.22.168 has introduced an option to record phone calls (finally! thank you Jolla!). However, no matter how I try, the resulting recordings are always silent. I tried pressing the button immediately after dialing, immediately after answering and half way through the call and the result is always the same: a recording of the correct length and with the correct tags but silent.
I went as far as inspecting the recordings in a binary editor to see if this might be just a playback issue but the files are genuinely full of just low volume noise (the values oscillate just one or two bits around zero).
I had dpurgin's Call Recorder installed before and thought, maybe there is a conflict. But uninstalling it and rebooting the phone has made no difference.