Hi Sebastian,
I just thought of something! When you open more than one instance of EA Studio you cannot leave them as tabs in the browser. You need to separate the tabs into individual windows. When left as tabs when you switch tabs the Reactor in the first tab will stop working and the Reactor in the open tab will start working. In other words, the Reactor will only work in the current selected tab in the browser. To get all the Reactors to work they need to be running in separate browser windows.
Alan,