I just ran into the same issue. Everything was working fine--I was able to zoom into my toolbar images to 3200% with no problems. Then all of a sudden something changed and when I zoom in, the artboard appears gray and if I select an object, I see a distorted outline. Zooming out eventually results in the objects appearing correctly. After checking a lot of things, I realized that I had changed my artboard size to create a toolbar image strip. In my case 1920px x 16px. Previously, I had my artboard set to 16px x 16px. It was the changing of the artboard size that causes the artboard to appear gray. If I reduces the width of the artboard to 200, then I am able to zoom into 3200% without any display issues.
I just ran into the same issue. Everything was working fine--I was able to zoom into my toolbar images to 3200% with no problems. Then all of a sudden something changed and when I zoom in, the artboard appears gray and if I select an object, I see a distorted outline. Zooming out eventually results in the objects appearing correctly. After checking a lot of things, I realized that I had changed my artboard size to create a toolbar image strip. In my case 1920px x 16px. Previously, I had my artboard set to 16px x 16px. It was the changing of the artboard size that causes the artboard to appear gray. If I reduces the width of the artboard to 200, then I am able to zoom into 3200% without any display issues.