I have simply tried to be responsive to your questions. Sorry I have not been able to be of any help.
Previously
Now
For this one could try the app Checkup (aka Fairphone Checkup) to see whether any switching between primary / secondary microphone shows up at this level.
Hello, from what Iāve been told by the people I spoke to on the phone in the last couple of weeks the problem seems to be gone for me, after upgrading to 3.3. Iām not sure if the problem could be somehow carrier-related then (as if in subsequent updates they were fixing settings related to e.g. VoLTE that as far as I know are specific to each carrier), Iām from Italy and my carrier is Coopvoce (Vodafone network), but I donāt really know.