I’d vote with the connections under the seats.
First things first thought before you go delving into it all. I’d advise you to disconnect the battery and leave it disconnected for at least 10 mins before playing with the plugs.
The air bag systems work of piezo Chrystal and it only takes a milivolt to set one off. So any residual voltage should have gone after 10 mins or so.
Having said there are many people that have disconnected plugs and reconnected them without any issue. I’d always advise against soldering air bag wires. Best to make sure that the connectors are clean and corrosion free etc
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