Had a customer call in the other day and complain about this. Selecting something new in the dropdown doesn't always select the item clicked on.
If you move to the selection and your mouse moves off the dropdown area when you let go of the mouse button, your click will not select the item.
If you move to the selection and your mouse is still over the dropdown area when you let go of the mouse button, your click will successfully select the item.
So, we let our customers know they need to stay within the lines, as they learned when they were coloring.
Have a good one, Tracy