Does anyone know why this happens? This is a MacBook Pro late 2013 Retina attached (but not pictured) to a Dell Ultrasharp 27” monitor. The distortion appears frequently, but will disappear the moment you roll a cursor to the display or move a window to it. It will happen when open active windows are shown on the display, but disappears when you move or change something. In my opinion this probably means that something on the logic board is slowly decaying, because this happened to a MacBook I had back in 2008. That Mac died right in the middle of a remote project. I am planning to get a new MacBook anyway. In any case I would love to hear from anyone who knows what this problem actually is. Has anyone seen this? I have not seen any discussions or pictures elsewhere.