Script Action Weirdness

I am going through the Inductive University courses. I am at Perspective Components and Bindings, Script Action. After the training script was modified to increment by 5 when the shift key is pressed, as the navigate_next icon is pressed, the label sometimes flickers to have a blue background. I believe my view and script are exactly the same as the one used in the course. When I increment by 5, at times the background does not flicker to blue, but it changes to blue and remains there. Is there a reason for this?