Geant4-DNA, chem6

I use chem6 (in /src/geant4.10.07.p01/examples/extended/medical/dna/chem6).
I want to add two new chemical reactions, which I have done in
But the problem is that the reaction occurs only if we put the diffusion coefficient to 0 m^2/s. For the first reaction, it can be correct, but not for the second reaction.
Do you know how I can make the reaction to occur without having to put 0 m^2/s for the diffusion coefficient?

Thank you!