The other day I replaced a few parts on my SE. I put in a new battery, screen (swapping in the home button from old one), and the Lightning port (includes microphone).
For some reason, now my phone doesn't seem to understand my voice anymore. Siri only seems to hear after the first word or two (but clearly then), and dictation doesn't hear me at all.
I was very careful to position the mic correctly on the new lightning connector part, and I apparently sound completely normal on phone calls and FaceTime. Voice recording seems fine too.
Could this be related to something other than the mic?