Since Vaadin 8 Version you can only crop one time.
You can see it in your own example with Chrome: https://vaadin-jcrop-demo.rocketbase.io/
In an earlier version of the addon after you draw a rectangle you can still change the size and the position. This isn't possible anymore. It seems that toggle gets disabled somehow. This should not be the default case.
Since Vaadin 8 Version you can only crop one time. You can see it in your own example with Chrome: https://vaadin-jcrop-demo.rocketbase.io/ In an earlier version of the addon after you draw a rectangle you can still change the size and the position. This isn't possible anymore. It seems that toggle gets disabled somehow. This should not be the default case.