PhysX shapes fall through collision geometry

[Viper]

I am having a problem with PhysX shapes falling through collision geometry. After shapes collided with ground object some time later they start to fall trough the ground. I don't know what parameter I have to tweak to prevent this. Can someone help, please? I use tyFlow v1.126 currently. 
Here is the video of problem.

[Viper]

After multiple attempts I was able to fix this problem by changing 'Penetration offset' from -0.01m to -0.001m in 'Collision tolerance' of PhysX Shape operator.