I could be wrong but the seatbelt sensor I'd of thought is connected to the seatbelt buckle(?) rather than the seatbelt itself.
I drowned mine in February and literally stripped the interior out including seats, belts and sensors and the main srs computer to dry it out and all it required was an auto sparkie to clear a couple of faults to reset the airbag light.. Probably a certain amount of luck thats all it needed to be fair..
As mentioned the clock spring/spiral cable is a very common cause for common cause too.
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