normal 3dgs Physics - Box and Sphere only work proper. All other types are buggy.
Instead use Newton with Lite-C. Very stable and supports, Sphere, Box, Cylinder, Cone, and Convex hulls and some others too. Ventilator has implemented the wrapper for it.
A better choice would be to use Ageia Physix, but cant find any wrapper for it. Though there is a wrapper in blitz3d. It supports Cloth and water too. Hope to find that somebody wraps it for 3DGS.