There is more to this problem than meets the eye.
My problem emerged with Shared albums, which I like to watch on my TV courtesy of Apple TV and iPhotos.
When you import an image from media, eg USB stick, the files come across with what appears as all their meta data, ie Title, Date and Time taken, Location etcetera. This results in images that are sorted primarily by date/time and secondarily by a Title which is the image numbering system of my three cameras.
The issue happens when you try to import those images into a Shared Album. The titles do not come across no matter which way you try to import them, vis
a) Drag the images en-masse from the source Library area
b) Copy your images from the Library into a more logical Album and then from there drag into the Shared Album, or
c) With the Shared Album open, click the blue "Add Photos and Videos" button and proceed with selecting and downloading.
What happens is whatever order you do the copying in, determines the end position of an image in the Shared Album. eg if you select and add a single image that may be at the beginning of your chronological journey, it ends up as the last image in your Shared Album.
I tried selecting all the desired images but 750 just conked out and did nothing.
Therefore, I am stuck with no clear solution. If only the metadata was imported into the Shared Albums I am sure would make a difference to the outcome.
I would suggest that this is a bug in the system and probably needs attention from Apple's engineers.
Cheer.