This has happened multiple times. The left touch screen will not react to touch or the mouse. in a plot, touching on a group square will show the group's fixtures in the programmer, but they won't give the blue highlight. Touching the fixture in the plot has the same result. 2 finger pinching will not work either. But, if I do a Pig Open Backspace, it will instantly correct the problem and the plot will jump to whatever size it would have gone to if the pinch zoom had worked as intended.