Bouncing window

Thank you for providing us an amazing game engine.

I’m afraid, there seems to be a bug, violent bouncing of some window.
I was using “ThirdPersonCharacter” in “ThirdPersonBP”, a default content in an Unreal Engine project.
Creating a new component, making it a child of “Mesh”, and trying to setting its parent socket as “head”, I found that the window to chose a parent socket bounced violently and couldn’t solve that problem, how annoying it is.

I would really appreciate it if you told me how to stop the vibration. Thank you for reading the question.