Hi Fairy Cardmaker,
We don't flip images during upload. We only shrink them, if they are too big. That's why its puzzling.
If they are too small vertically or horizontally, our system simply rejects them, and asks user to upload larger images.
It probably has something to do with the images itself. Maybe they were originally taken in a different orientation, and then flipped in the photo editing program? We won't know until we get the images and try to upload them ourselves.