The Frame around a Graphics part like ArrayPlot is not always complete. The Right and/of Bottom part are missing depending on the Image Size.Is there some explanation for this behavior? Can this be prevented?
Stephen Wolfram brought up this issue and others on a recent Live CEOing stream.
It may be a problem with screen resolution. What happens if you change the magnification of the notebook?
I tried to change the Notebook magnification. Problem persist. The Frame comes and go's when I zoom the Graphics window (click and drag corner of orange rectangle)
I am able to reproduce the issue by WL 13.2 on Windows 10 Home.
With Mathematica 13.2 on Macintosh the frame becomes fully visible when I reevaluate your inputs.