Local current density

Hi, I am working on a simulation of a redox flow battery. I used the redox flow battery model COMSOL provided and edited it a little.

I don't understand it fully and what puzzles me the most is that despite the lack of change in V2/V3-Concentration, the local current density at 9/10*H_cell is not zero. (1D plot group: local current density with 4 plots in it. 3 different cut lines, the last one at 9/10*H_cell should be 0 )

Can someone explain to me why that is?

Thanks