Many thanks PWFarnell,
I will do that the next time I am onboard & check voltage differences throughout the system. In another thread
I found that a busbar nut had come loose ( it must have been from engine vibrations ) - the next time I am onboard I will be checking ALL connections/crimps etc
In my head I imagine that connectivity is binary - it works, or it doesn’t but of course poor connections can give a curveball reading - not a false positive but the problem might not be obvious.
Many thanks again - I will keep you & this thread informed on an update when I find one.