Strange screeching sound during calls, comes and goes
I have an iphone 6 Plus and sometimes during a call (happens randomly), It begins to do this weird high-pitch screeching and then the microphone stops working. I have gone ahead and replaced the top speaker and also the lighting cable/headphone connector piece so far and it still happens every now and then. It does go away when I restart the phone.
Maybe the lower microphone?
Started happening again. I cannot hear or speak when trying to make calls. Went and did a few more tests, I can watch a youtube video and also listen to my voicemails both through small and loudspeaker so it probably something you mentioned above.
Tried DFU restore and we will see. Not too sure how to repair baseband circuit if even possible.