Correct. do not solder wires on a VW, they don't like it. Airbag wires are especially sensitive. The way i was talking about checking the buckle can be done without taking out the seat. fold the buckle all the way left, all the way right and look where the wires go into the bottom of the buckle, if the wire is actually broken, you should be able to see it right there where it goes into the plastic body of the buckle.
When they break there, there is no good way to fix them. Just to replace the buckle assembly.