If I create a new gallery post, hit Upload Images, and then select images that are already uploaded, they get added to the post content but do not appear in the top preview box. However if I hit Upload Images and then upload new images these ones do appear.
I noticed a similar issue is in the changelog under 1.0.2:
Gallery is displayed as expected when images have already been uploaded before gallery tab is selected
However I am using 1.3.1 and still experiencing this issue.
If I create a new gallery post, hit Upload Images, and then select images that are already uploaded, they get added to the post content but do not appear in the top preview box. However if I hit Upload Images and then upload new images these ones do appear.
I noticed a similar issue is in the changelog under 1.0.2:
However I am using 1.3.1 and still experiencing this issue.