Chosen Solution

I replaced my screen. After the replacement the microphone does not work anymore when I put the phone in speaker mode. Does the phone have a separate microphone for speaker mode? Or is it the same microphone? I would think there is only 1, but then this is a very strange issue. Any thoughts on what I should do/replace to solve the issue?

There is a 2nd mic for speakerphone and related apps. I wouldn’t be surprised if you proximity sensor is also not working too well. Its a pretty cheap part and a really easy fix: iPhone 6 Front Camera and Sensor Cable