Paint missing I think would tell me she may have been bumped and repaired. Only a dealer with the computer star system can reset the air bag light which is another indicator it may been repaired. If they unplug the airbag to get into the door it will leave a light on. You have to unplug the battery positive cable before unplugging airbags. Did you know who owned it previously or buy from a car lot? If she took a hit in the door it may letting water into the electronics that are under that floor board. Take your carpet up and you will all the electronics under there. There's your radio problem.