Hi Mickey,
I took the whole bobbin winder mechanism while still attached to the guard off the machine. The little bolt and nut holding the winder to the guard wasn't exactly loose but it wasn't rock solid either.
Gave it all a clean/oil especially the spiral thread as you recommend and made sure the thread guide was all the way to the right before re-affixing the winder to the guard (securely!) and then putting the whole thing back on to the machine.
It is all working just fine.
Many thanks to you (and other contributors)