The injected current is flat, but the secondary current may not be. However, the metric that follows from both the primary and the secondary current is the Collector Efficiency.
If the Collector Efficiency has not settled, try the following:
Reduce the cycle-to-cycle averaging factor. The averaging factor often needs to be less than 0.5 for higher density meshes using the quadratic field solver.
Increase the number of particles, if the particle count is too coarse.
If the Poisson solver is not settled, the user should try the following:
Add more cycles if the trend is decreasing.
Reduce the Poisson Solver Tolerance.
Increase the number of particles injected.
Improve the mesh in the injected region.
Consider a quadratic field solution, with perhaps an even lower Poisson Solver Tolerance.