wrong actionMethod called when closing window

Dear All,

in one of our WebDypro Application there is a pop up when I click the windows "close cross" (see arrow on the below picture ) another window is being opened instead of closing.

How can I find out (fix this issue) why the wrong action method is being called.Where is the event handler being set in general, how can I set the correct eventhandler or call ON_CLOSE action.

Thanks in advance

Alex