If the user clicks on the spin box that has an On Mouse Leave event and then drags the mouse around the leave event will fire off as if the mouse position is still being updated to the screen (the mouse is hidden when clicking and dragging on a spin box). This causes two issues.
Issue one: There is a continuity error because the mouse enter event does not fire during this error, only the the event leave. Meaning that you can have multiple leave events firing off without a ever getting a mouse enter event.
Issues two: The mouse when release always shows up as the spot that the user originally clicked on the spin box. This means the expected behavior is for the event leave to not fire off while using the spin box
Head over to the existing Questions & Answers thread and let us know what's up.