Once the first graph is displayed

1. move the viewport (not the nodes)
2. zoom out
3. press the "fit" button (which used to be zoomExtent) - works fine!

Now 

1. click the "click me" button (at the very bottom below navigation buttons)
2. the datasets will be cleared and a second graph will be displayed
3. Maybe wait a few seconds before the stabilization event is fired and the graph is fit again (actually this step is not necessary)
4. press the "click me button again to switch to the first graph
5. try to fit the graph by pressing the "fit" button (which used to be zoomExtent)
6. Neither does it correctly centerize nor is it zoomed (streched) correctly!