Sub window closes on any button click event

Hello,

Im gettting started with vaadin attempting to build a multi-view wizard functionality inside of a sub widow.
After adding a “Next” Button with no click handlers to a vertical layout, clicking on the button automatically closes the subwindow. Is there a default listener the API adds that dispatches a close event? I used
setClosable(false);
to hide the default close button but the window closes regardless of where the click originates.

Thanks in advance,
Tod