I have been recently having this problem. I work from home on AutoCAD LT 2021, but recently when I use it, when I drawing in a file it turns my secondary monitor black. It does not turn it off though, because I can still drag things onto the black screen. The screen will promptly turn back on when I either click out of AutoCAD, turn off AutoCAD, edit the text in AutoCAD, and use the file explorer to save files. Does anyone know a potential fix to this?