iPhone 5c Bottom Microphone Static

I bought my roommate's iPhone 5C off him the other day, and everything was fine for 2 days, but then I had to replace the Display assembly, and since then my bottom microphone sounds like a metallic static mess when I use Siri, and record front facing videos. I'll try to upload a sample later on.

I've tried replacing the dock connector assembly 3 different times, with different units every time, and still no luck. The headphones, charging jack, and speaker all work perfect.

The weird thing is, Voice Memo, the Google app, and Facebook Messenger, can all hear my voice fine, and I'm not so sure it's using the rear mic, because when I tap on the bottom mic from the outside, the waveform spikes, which means it can tell I'm tapping, thus it can hear me.

It's been really well taken care of, the previous owner was extremely careful with it, and had put a 2 inch Otterbox on it, and as far as I know, there's no damage of any kind, and I didn't see any reason to think it had any, when I replaced the screen.

Any help is hugely appreciated,