In quantum physics there is the a phenomena known as the Observer effect, aka the Hawthorne effect. It refers to changes that act of observing will make on whatever is being observed. This effect is a regular occurrence when working in system administration, particularly on the help desk.
You don’t have to work in IT very long before someone will tell you that their computer starting working “just fine” when you showed up at their desk. This is the Observer effect in action.
When a support persons appears to troubleshoot an issue and asks an end user to recreated the problem, the problem will not occur. This is most often because the end user is now paying attention to what they are doing and aren’t making the same mistake they were making before.
This effect manifests itself in the opposite way as well. I’ve gotten the occasional call stating that an end user “was doing something all morning, but now it’s not working.” When asked to recreated the problem, it usually becomes apparent that the person has suddenly begun to pay too much attention to the steps they are taking -thinking too much about them and stopping too soon in the chain of mouse clicks or key strokes to finish the action. Instead of being observed by an outside party, the user has suddenly become the observer themselves and changed how they perceive what they are doing on the computer.
Either condition results in a help desk ticket, the observer effect either causes the problem or helps to solve it.