Collision traverser

I created a np = Nodepath(“xxx”), and attached a bunch of nodes to it. Each of the node has a collision box child. Then, I set one of the collision box as the collider and traverse(np).

The objects are in collision but the system failed to find one.
If I replace traverse(np) with traverse(base.render). The system reports a collision. (np is also reparentTo(base.render)

Is this considered to be a bug?
The document says dont use the parameters of the traverse function though

I think the argument to traverse(...) indicates where to look for into colliders, not where to look for from colliders (since those are explicitly added to the traverser), but I could be wrong.

Is that what you are seeing? Or are both your from and into colliders under that NodePath?