Thanks all, correct about HB’s - cracking pick ups.
Someone else chipped in with some sage advice on a pm.
i rechecked connections, made sure pins are not bent, the wires were a bit compressed (suggested by another) so I made them more of a gentle curve.
did that and back on track
You both may be entirely correct about loosening with vibrations, seems the most plausible, I suppose I didn’t want to cut a cable if I didn’t have to, but it’s no biggie and will be good for me to get soldering!
Interestingly my other Hohner, fully passive has the other jack, and would have been no bother, bloody barrels!