Images getting resorted

Hi

For some reason the thumbnail images are getting resorted every few days. We upload only an image a day, which used to go at the bottom. But now the order has been changed and the new images go anywhere but the bottom. We haven't touched the script since install, so we know that isn't the issue. Even when we go into an older month's folder, the images are now out of order.

Is there any explanation for this? Or better yet, a fix??

Thanks

i don't believe they were meant to be uploaded in a specific order