motion controller is unable to grab when the Gamepad Event is added in open level BP

Hello, can anyone please help me with this problem?

I’m using HTC Vive.
Normally, when I press the button of the controllers, the hand will play the “grab” animation.
But I realized every time when I add a “MotionController(R)Trigger” event in the open level blueprint, the hand is unable to do the “grab” gesture. (it still can pick things up, just can’t play the animation)
Here’s an image to demonstrate what I mean:

And the blueprint that I made:

I’m wondering if other people have encountered this problem too.
It really bothers me. All I want to do is using the gamepad event to trigger material transition.
If anyone knows the solution of this problem, please tell me what to do!!
And thanks in advance!