collide Surface_Kangoroo_bouncing particles between surfaces

Hey,

I try to let particles bounce between 2 surfaces using collideSrf plugged into forces combined with a UnaryForce for the starting direction. Instead of bouncing off the surface the particles are going through the surface. What am I doing wrong? If I am using a sphere the particles recognize the boundary but stay at the outside of the sphere instead of bouncing. Or do I misunderstand the function of this component?

Thanks a lot,

K*