My guess is the squib connector for the airbag is damaged on the door from someone not disconnecting it properly. You say it snaps right in place? There is a certain procedure for disconnecting that airbag connector and should not simply plug in. Check the video link below and pay attention to 8:55 into the video for the correct way to disconnect the connector.
https://youtu.be/P93ucj8mMyM
Also her is another link to the squib connector and how it works. You're codes lead me to believe this is what you have going on.
https://forum.e46fanatics.com/showthread.php?t=680542