I suspect that this is something BMW would step up and goodwill because of the safety nature. Worth having your dealer try.
FWIW- the airbag light in my 528i comes on periodically, stays on for a few weeks, then goes out again. Dealer says its the passenger seat sensor, and probably becuse someone put their weight on the seat with their knee which will damage the sensor.

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'04 E53, 4.4 Sport
'97 E39 528i
'86 911 Carrera, track car
'96 BMW R1100R