The buttons on the toolbar are enabled or disabled based on the current selection.
But, after selecting a link, if the link is moved to a new position, the buttons are not enabled/disabled accordingly.

example (screenshot): if a link is at bottom of the list, when selected only the "Move to the start" and "move up" button are enabled. But if you clic the "Move to the start" button, the buttons are in the wrong enabled/disabled state, as you can only move that link down.