I double checked the contact (snap in) behind the airbag, it is securely in.
Clearly, however, the contact spiral was displaced as part of the repair, so if it was weak to start with, maybe it is now broken.

Will the codes actually reveal which component is at fault -- ie belt buckle vs. contact spiral?

Thanks.

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2008 S550
2010 GLK350
1997 E420 (retired)
2005 CLK500 (retired)