Bullet physics air density

in the soft sphere example from bullet physics…
when i reduce the air density to a very low value, say 0.0002… some of the spheres fall on the ground and just collapse!!! (the mesh collapses inwards)
why does it happen this way?https://vvvv.org/sites/default/files/imagecache/large/images/bullet.jpg

also, if there is enough force/ tension, the rigid bodies pass through soft patches…
i anchored the soft patch and let a moving rigid body collide with it by giving it some velocity… ( rigid body of zero mass to prevent action of gravity)
what am i doing wrong??

Can you post the patch?

@Urbankind… _/_ sorry for the delay…
i have just changed the air density and mass of spheres…

Soft_Sphere test.v4p (29.1 kB)