Collision3D event.contacts[] sometimes empty onCollisionEnter?

Hi, I’m using Creator 3.8.2 and trying to find out the contactPoint when 2 colliders collide
The docs said that I can get the collision’s event.contacts to get contactPoints, but my test code sometimes return an epty array of contactPoint for “onCollisionEnter”

Is this a bug or I need to try “onCollisionStay” (which occurs repeatedly) ?

I do want to get the very first contact point of the collision, but “onCollisionStay” might give me the late result when the node of collider moves a bit