Be careful to clean the corner 2,3 mm screw next to backside camera
I had my display shattered, but the followup problem was the microphone not working/working erratically during phone calls.
iFixit did have a guide for the second step too and I now seem to have fixed it. I cleaned the screw and holder with some spray and compressed air.
a sticker was in between from somewhere.
I took that to the side and it seemed to work