How to repeat:

Comment overflow: auto;

and

comment height: 200px;

in ui.droppable.html (demo file)

.droppable {
     float: right;
     width: 200px;
     //height: 200px;
     background-color: #e9b96e;
     border: 3px double #c17d11;
     padding: 5px;
     text-align: center;
     //overflow: auto;
     opacity: 0.7;
}

Fill the droppable object with draggable objects until it increase its height by several times. With increased height droppable object ignores draggable.