[Longespee]

Have you looked at the weights, there are three points where they add it, I can see the glued spring weight opposite end of the needle.

I had the same problem as you had, a very clean and healthy machine, with internally clean meters, Martin helped me with a great many emails to and fro, eventually we managed to get everything working with shunts, but I was never happy with the result.
I then spoke to and old friend who after me explaining my problem and how can a meter that was basically untouched be so out of spec?, his first question was '' Were there what looked like Bird droppings in the meter when you took it apart? '', '' yes'' I replied, they were more like microscopic egg shell, but still debris, he said '' those bits were your meter weights, we used a kind of Tungsten paint years ago, which is why I asked as it falls off sometimes '', he then explained how to balance check the meter and adding some modelling paint to the points the meters worked perfectly.