That is a bizarre issue. I think it is a metadata property for the image for something like a non-destructive display rotate used in apps like picture viewer, RAW or Adobe Bridge. I have encountered something similar before but don't remember the explanation - just the simple cure.
Out of curiosity I downloaded the image. Uploading it into a standard image container produces the same result. Loading the image directly into the browser shows the image upright (guessing the browser knows how to interpret the property). So, I opened the image locally in preview (mac) and simply resaved. The resaved copy is upright every time and should cure the issue for lightbox as well.