Hi, I am kimmie's other half. BTW the NSU is behaving exactly the same before and after loctiting the fasteners in. The NSU bolts were not coming out, but they certainly were not tight at all.
I traced the loom from the bulb back to where it enters the crankcase. All the connector contacts are clean and no amount of wiggling and bending of the wiring loom will get the bulb to go out (at least while the bike is cold).
I also cleaned the NSU contacts when I loctited the bolts in. The sensor was in good shape. The wires were sound and the "potting" was intact. So I am thinking that replacing the sensor is the next step.
So has anyone heard of the issue with NSU not working when hot?