The hierarchy is exactly the same as your screenshot. There is no other event involving these collision boxes.
The car with bike is moving along a spline actor. I write down related functions in BP editor by myself. It has no problem.
The other (except the car with bike on it) are from a package called “traffic AI” system. Traffic AI System in Blueprints - UE Marketplace
They are spawned on specific points and follow splines to move. Unlike the car with bike, here everything (except the box that I added) is already prepared in the package. However, I found that these cars sometimes would have sudden brakes/shakes (see the red car to the right) and then the dislocation happens. I think the problem may be solved by either stopping such shaking behavior, or disabling the dislocation. I’ve already emailed the author about this shaking phenomenon and am waiting for a reply.