Excuse me my English, I only take a internet translator.
Had the same problem,
tried second level Apple support. After their conversation with many tests, we came to the conclusion:
-The problem is not iOS error (not only in my iPhone 5 with a 6.01 and iPad 2 with 6.01 but also with iPhone 3 g with 4.2.1 it occurs) or iPhoto error but an iTunes bug.
-Also occurs when some photos that were made with a single camera. But mostly for photos with two different cameras.
-When you synchronize it with iPhotos events it can at occur not avoid, because the events are sorted always date and time.
-Workaround if you use Mac and iPhoto. No idea with Windows syncing photos in a directory:
Create albums, for example from the event in the library to create an album.
Then there is the album as well as the events sorted by date.
Now switch to manual sorting, e.g. through moving image on position 1 to position 2 and moving then back on position 1.
This is the sorting (iPhoto menu, photos sort) set to manual.
You can also just above the menu in iPhoto, sort photos "by date" switch to "Manual" but sometimes the pictures are then sorted totally messed up.
So rather on display, sort photos by date or time so set and then move a picture in this album to a position immediately back slide and. This will be converted to manual sorting.
Then, the photos in iOS devices are displayed correctly.