gray rectangle outline on macbook air desktop

*note: I tried toggling the "show preview rectangle when zoomed out" option under accessibility and it did not fix the issue.

the rectangle only appears to be on the desktop, meaning I can move windows in front of it and it disappears. I can't click on it or select it or move it. I can drag folders in front of it, which obscure it while im holding on to them, and the folder goes behind it when I let it go.

its running high sierra 10.13.6