The flashover I refer to may occur in hi tension ccts and can be visible in very low light. Having looked under a few hoods / bonnets sometimes you can see where the electricity is leaking out.Picked this up from old WWII heavy piston guys years ago.
I dont think this is the problem and this kind of testing is not routine.
But I do think it maybe a combo of bonding and perhaps some shadowing.
I'm not betting my gonads on it but am very interested in the fix to further my knowledge.Could dig me out of the poo sometime!
I am avio and have reasonably wide experience also a ham operator.