In our forum if you visit a post with one or more pictures attached to it and you try to open the pictures they open and can be viewed ok, however when you are done and try to close the photo it closes but then there's still another one in the background that you must close as well before being able to view thread normally without the gallery.
I hate disabled all plugins and tested this in both our live and our staging site with the same results. I have attached a small vid so you can see the issue. You can also visit the following URL to see the problem yourself.
Thanks a lot in advance for any help provided.