Kevin.
Actually, if I knew how to replicate it, I had waited a little before to post this, hehe.
I know how to prevent it.
If I save the whole thing to my computer (e.g. Safari.webarchive extracted with WebArchive Extractor app) and it loads all the images faster than the warnings take to appear, it loads "better", still not always fine.
It certainly fails when any javascript error happens, even if not from this script, and some other reasons I don't know.
The "expand" link manually re-triggers the function which rotates the images, that's why it works.
So it could be the "load" function, but I'm not good enough to tell. Could it be a lack of callbacks for different errors?