When running the code below your presented with a window containing 6 checkboxes, one of which is ticked. When item 2 is unticked, a red outline is placed around all fields. If the mouse is then moved a significant amount, a tooltip will be shown saying "You must select at least one item in this group". If the mouse is moved and an item clicked before the tooltip is shown, the red outline disappears but the tooltip is still shown shortly after. I believe the problem is because the tooltip uses a show timer which is never cancelled.