Widget blueprint and array addunique, not working as expected

First, here is this blueprint:

And here is what it looks like:


What I’m doing is add the text in this Textbox to an array, every time I click that Button, but after first value added to that array, anything I input afterwards will not be added to that array, see that blue output text? only one “a” in it.
I’ve no idea what went wrong here.