Poor Audio from the door v2

Hi, I have just installed the v2 door bell. Al is great, video is good, audio from the person on the phone to door bell, person at the door is fine. However, audio from the person at the door to the phone is terrible. If the person at the door gets right up to the door bell I can hear them, if they stand on the door step,, and talk normal volume I can hardly hear them very very quiet. Is there anything that can fix this or is it a fault unit? Thanks Andy.