cast success in level blueprint but fail in character blueprint (when reopen the editor)

My project is a full new FPS template and I make a small plugin which only contain a QxGameInstance class(inherit from UGameInstance)

And I set this class(QxGameInstance) as my default GameInstance in ProjectSettings

Then I made a simple cast in my level blueprint it works fine,whenever,like this.

If I do this simple cast in character blueprint ,for the first time ,it still works,like this

But,If I close the editor and reopen it and open the character blueprint again, it goes like this

Yeah,I do nothing but close the editor and reopen it, and meanwhile ,this simple cast works in level blueprint.

Do any guys know the why?
Thanks a lot