Hello,
I also have this problem like many others and for me it started a few months ago. When I record a voice memo or make a video with the camera the second microphone doesn't work.
First I did send my phone two times to the repair service of T-mobile, but they 'Couldn't find the problem'... Then I decided to send it to Microsoft and I hoped that they would fix the problem, because they know their own phones better than T-mobile and
also know about this issue. In the description I was very clear and I said like 3 times that the SECOND MICROPHONE isn't working when recording videos or making voice memos.
Today I received my phone from repair and guess what? They didn't do anything, only a functional test... So I tested the second microphone and it stil isn't working! I just don't understand why they didn't repair my phone, it's a well known problem and I
made it very clear that my second microphone isn't working.
I'm very frustrated right now, I made a phone call to microsoft and they said that I have to send it again for repair to them. I did already send it 3 times for repair and I still have the same problem...
For me this was the last time that I bought a Nokia, Microsoft doesn't care about us and if you send your phone to them for repair because your SECOND MICROPHONE isn't working, they wil do NOTHING.
btw. I live in The Netherlands and I had to send the phone to a German repair center.