Tap Request microphone; note whether iOS asks, and what the log says about the track.
Record each sentence once: Record, read it, let it auto-stop (or tap Stop). Then play it back with the player (does it come out of the speaker, at normal volume?) and Upload take.
Turn on shadow mode for one sentence: the reference voice plays while you record. Note whether you hear it from the speaker or the earpiece, and whether playback got quieter when the mic opened.
Switch the audioSession mode and repeat one take.
Do the whole thing once in Safari and once from the Home Screen icon.