This is largely correct, but a few addendums. The problem has been around for nearly two years. It has been looked at by the dev team, but there is obviously some blocker they are unable to overcome. :( There are two solutions and one workaround. Solution 1: Switch to Firefox Solution 2: Set the default behavior to not open in an external window (default can be at under the in-game settings tab. Workaround: While you are focused on one of the external windows, instead of closing it, refresh or reload the pop-up. It will close and can be re-send again in the same session.