Fairphone 3 microphone issues

I have the same issue since I bought the FP 3+ and right away installed /e/OS. Since the FP 3 is sold with /e/OS preinstalled, I hoped to get this issue resolved fast. Maybe more details help to debug it:

Settings

  • Network carrier: Congstar
  • Device: Fairphone 3+
  • OS: /e/OS 0.23-20220406175185 (Android 10) [but I have the issue since bought the phone and installed /e/OS 0.13]

Symptoms

  • When making a phone call, at some random time (but usually within the first 5 minutes) the other person tells me that I sound like I would be very far away. The issue disappears after a few seconds (but still already interrupted the flow of the phone call) and reappears several times during a call (depending on the length of the call).
  • I, on the other hand, can understand the other person perfectly throughout the full call.
  • The microphone seems to work fine during Telegram calls and Signal calls, but not with the official phone app using classical phone calls.
  • It is indepedent who initiates the call
  • It happens for all network carriers that the people have that I call (including landline).
  • It happens when using 3G, 4G, or Wi-Fi for making the call.

What I tried but did not work

Is Fairphone aware that the problem still persists?