Ubiquitous airbag fault - tracing actual problem

Hi,

So on my Mini one 2002 - I have the usual airbag warning light on and using my trusty B200 reset tool I can trace the fault to the passenger side pre tensioner area.

Now the question is what bit - the blue connector under the seat (the usual suspect) or the actual pre-tensioner itself or maybe some other part of the wiring/system?

The reset tool does work...but then at some point in driving (with no one else in the car) the light come back on.

Does anyone know how to check components in turn (short of buying new ones and trying) to narrow down and hopefully solve the issue.

I was toying (for investigative purposes only) with switching the blue and yellow plugs over - and seeing if this gives any more clues (the fault maybe could give "airbag" so showing its the pre-tensioner - if you follow the logic,

Any views on this or other clues on tracing the fault?

T1EAK