Why is GoPro not recording any audio?

Anyone have any idea as to why the gopro would not be recording any audio? None of the film clips will have any audio. I tried using an external microphone as well. The external mic was able to record audio, however there is a cracking/popping noise on about half the clips.

Would this be a microphone issue? Is the microphone on the main board? Are the onboard mic and usb mic connected somehow? Since the usb microphone only works properly half the time, could the be a problem with the entire board?

Any ideas how to troubleshoot?