The logic of this is that it requires me, my location and this guitar to manifest the problem. Substitute any of these and the problem goes away. Looking around various forums I note that these circumstances do arise for a minority of other folks also. Is this something that Gibson should be responsible for mitigating, or at least warning prospective customers about? Oh, hey maybe that's something to debate another day. I know, I started it but life is short, etc.
What I've since discovered is that if I grab the central heating radiator in the room where I'm playing the problem disappears. Here in the UK central heating systems are grounded. So I've ordered an anti-static wrist strap which I'll tether to the radiator when I'm playing. It's not a cool look but I'm pretty sure it'll work. And then I just wait for the nitro to do that which I'm assured nitro does.
Thanks to all for your input. Tin foil hat anyone?