Kangaroo Box (brep Solid) collision with Ground (Brep Open Srf) need help T_T

I am trying to simulate a bunch of "boxes" (Brep Box) falling onto the ground (brep open Srf), bounce for few times (with bounciness applied to the box) and eventually slides off to the lowest point on the srf. I have made some definition based on simple tutorials on the net, I got a very strange result. 

1. It takes the box forever to reach the ground surface, even though I set Unary force similar to earth gravity 9.8. or maybe is it just my limited RAM?

2. Some boxes "Jumps off the screen" and mysteriously disappeared. yet it happens while they are still "Falling" in the "AIR".

3. Simulation stops after all the box disappeared.

I wonder what went wrong. obviously there is something wrong in my definition but I don't know how to fix that after hours of frustration, or maybe the rumor is true there is a dark side of physics in kangaroo. I dunno T^T

pls see attached

hope to get enlightenment from you guys