2016 Kia Sedona air bags problems

My mother and her friend were driving approx. 35 miles per hour when the right rear wheel went off the road causing them to go into the frying pan river in basalt, co. There was approx. 42.1 degree slope. My mother was the passenger. We retrieved her pictures and video. She was video taping with her cell phone at the time of the accident. The passenger window was down. She said, "oh [xxx]", and appeared to reach to remove her seatbelt. They went into the river.

Airbags - the sensor light keeps coming on at random times, then will turn off for a few seconds, then come back on. There is not one certain thing that causes this (ie bumps, breaking, acceleration, etc). Not sure if this is a bad sensor issue or what it could be. Seatbelts - front passenger side seatbelt will 'lock' into place while driving (like after you would stop suddenly), and the only way to undo it, is to release the seatbelt.