When I'm viewing file gallery widget in admin post, I can drag and drop the images around any order I like, but they don't get saved. The minute I hit 'update' on the post, the images just go back to the original order.
If I click on the gallery picture in the contents window and select the mini gallery icon in the top left, I can open wordpress's gallery modal. it seems I can only change the ordering of the images here, but not in file gallery's widget. Could it be another plugin negating this?