Why preview is showing a black box instead of an image?
I had a similar bit slightly different problem. I had whole pdf pages that were turned black when zoomed in and were correct when zoomed out, but the zoom made them impossible to read. I found this fix https://tidbits.com/2018/01/30/fixing-pdfs-whose-pages-render-as-black-rectangles-in-preview/ basically you have to calibrate your screen. i did it and it worked first time. odd.