Spinner keeps changing after losing focus

When navigating a spinner with the keyboard, if you exit the field using the [Tab] key while at the same time the [Up] or [Down] arrow keys is pressed, the spinner keeps going up or down indefinitely.

It only stops when gaining focus again, or if the form itself gets focus, or hovering over any of the little arrow icons.

It seems as if the increment event is being raised continuosly, as the value displayed grows exponentially (the more time passes, the fastest the value increases).