Thank you all to reply,
Looks like a complicated problem. I just have found a post has the same question & in the very similar Pin Ball game project.
BTW @LeXXik Where can I use the following codes?
app.systems.rigidbody.fixedTimeStep = 1/120;
app.systems.rigidbody.maxSubSteps = 20;
Any guides can show me how to use them?