I have the same problem with the mics.
Im using a Lumia 930 with Windows 10 mobile updated.
When recording a video, the microfone works, but i noticed that left channel is really low, right channel is good.
It works fine for calls, but i cannot use to record anything, neither i can use the speaker when talking to someone.
Im sure its a software problem. Maybe MS could just turn on all mics on Lumia 930 for speaker calls and other apps, or just give us an App with a option to select the microphones we want to be used.