Thanks for the heads up Evan - it could be a one-off which sometimes happens if the token has expired (for example, if the page was loaded a long while before the image was posted). If it happens again, let me know and I'll take a deeper look .
I will try and do the post again. I just checked the size of my pictures 2448 x 3264, 2.64mb each. And 6 images. Maybe it was the size of them that caused the issue. I shall resize them and try again.