iCloud not uploading photos

Last night my iPhone 5s decided to re-boot itself, and re-arrange my camera roll into a random order (they have always been chronological). I wished to re-arrange them by transferring them to my PC, put them back into chronological order, and then place them back onto the camera roll via the ''image transfer" app. However transferring them onto my pc didn't work. So I'm trying the iCloud method.

I've attempted to upload my photos into iCloud (which has 20GB storage), however it keeps stopping at 2,565 photos. There is more than enough storage for the photos, so I'm unsure why it keeps freezing at that point (see screenshot).

Any advice on how to upload onto iCloud / put photos back into order?