Hi there,

Thanks for writing in!

The pictures are displayed in the order of how you selected them from the media library.

I have recorded a screencastto show the behavior on my end.

I request you check whether it may be a cache issue on your end by turning off any caching plugin and checking again.

Please let us know how this goes.

Hey Again,

Once you have selected the photos in the Media Library you can "Edit the selection" to fine tune how the images are to be ordered. 

See screenshot below: 

Thanks.