I replaced my graphics card (Mac Pro 5,1) for the Mojave update (RX580) and have a 27" Apple display with the magnetic power cable for my MacBook Air. I routinely use this to charge the MacBook Air. However, about a week ago, a very strange thing happened. I woke the computer from sleep and the graphics were highly pixelated. Only a restart would fix it. After some trouble shooting, I discovered that if I do not leave the MacBook Air on the ACD the pixelation does not occur. Any ideas what might cause this?