An issue about inserting particles in different boxes (Gengeo)

Hi,

I tried to build three boxes filled with spheres.

I inserted particles into the three boxes one by one (InsertGenerator3D.generatePacking). Every time, the particles could be packed into the first boxes successfully, but the inserting process did not work in the last two boxes (total tries: 0). Then I changed the order of the three box. The box placed first could be inserted in particles very well, but the rest two contain nothing.

How to solve this problem? How to insert particles into several boxes one by one?

Thanks in advance.

Zhenyu