I just took an hour of my time to delicately pick out piece by piece of my keyboard, clean the muck from under the keys, and place them back. (The desire to do anything but study leads you to do strange things…)
Have a look at what’s under “D”. Looks like typing a lot can produce unexpected side effects. And It wasn’t the most disgusting key, to be honest. Those who know Oompa can guess which key was the worst.
You should clean out the underside of your keys too, when your exams are in two weeks’ time.