In order to fix another bug, I had to use the filename as a "handle" to drag by. When you move your cursor over the name of the file, it should change to a "move" cursor, at which time you can drag/drop the image as before.
Simply click the "Save all changes" button to save their order.
Each image will have an "Order" field. The lower the number in that field, the earlier in the gallery it is. If you use the drag and drop sorting, this field is updated for you.
If images have the same number, they will be ordered with the most recently added last.




