TreeView vertical scrolling issue

I attached a netbeans demo project. I attached required fxml.jar too.
I am observing that the TreeView scroll verticaly properly ONLY if the scrollbar is at the min or at the max. In between, the scrolling is wrong and some non visible content is clipped and not reachable.
To reproduce, launch the demo. Choose a directory in the TreeView that has enough content to be clipped. You will observe the behavior.