Drag and drop an Anchor Pane onto the content view
Select the layout tab
Type a value into the leftAnchor field and hit return
Now click on the background of the content view to remove the selection.
The info panel briefly flashes "nothing selected" but then shows the info of the previously selected AnchorPane again.

I can get this to happen on the identity, look and layout tabs as long as you edit a property and hit the return key to commit the change.