Shaking, trembling behavior with touching arcade objects

Continuing the discussion from Selecting correct physics (engine):

When the balls reach the bottom and interact with the other balls resting there they start to shake and move weirdly. E.g.: They may change position with each other instantly etc. Here is the fiddle: https://jsfiddle.net/fselcukcan/ovy9c4bm/7/.

What can be the reason here? Is it normal?

Note: Click to create a ball. Click and hold to scale it up. Release the mouse to release the ball or it will release itself after a scale factor.
Arcade physics used here.