This study makes use of GARFIELD simulations to look at the dependence of the grid leak on the voltage of the anode wires.
The leak is measured between inner field cage and inner sectors (II), inner and outer sectors (IO), and outer sectors and the outer field cage (OO).

The voltage on anode wires was varied separately for outer sectors and inner sectors while keeping the other fixed.

The results are shows below:

The above plot is the result from varying the voltage in inner sector anode wires. The grid leak related to outer sector should not change because the only voltage change in these simulations are those on inner sector anode wires. Therefore the fluctuations in OO and outer part of IO leaks can be regarded as a systematic error for the inner sector grid leaks. From the constant fit we get about 2.7 % systematic uncertainty.

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Below is the same analysis but changing outer sector votlage and keeping inner at current nominal 1100 v.

The exponential fits are f(x) = a + exp(b*x).