Program: 36564
Project: 36564
Buggy source:
public FreeFormArea(FreeFormContainer con){
  super(con);
  root.getChildren().add(rt);
  setAnchors(rt,0d);
  BooleanProperty isHere=new SimpleBooleanProperty(false);
  rt.setOnMousePressed(e -> isHere.set(isHere(e)));
  rt.setOnMouseClicked(e -> {
    if (!isAltCon && (GUI.isLayoutMode() || !container.isUnderLock())) {
      isHere.set(isHere.get() && isHere(e));
      if (e.getButton() == PRIMARY && isHere.get()) {
        addEmptyWindowAt(e.getX(),e.getY());
        e.consume();
      }
      if (e.getButton() == SECONDARY && container.getChildren().isEmpty()) {
        container.close();
        e.consume();
      }
    }
  }
);
  rt.setOnDragDetected(null);
  rt.setOnDragDone(e -> rt.pseudoClassStateChanged(DRAGGED_PSEUDOCLASS,false));
  rt.setOnDragOver(DragUtil.componentDragAcceptHandler);
  rt.setOnDragDropped(e -> {
    if (DragUtil.hasComponent()) {
      int i=addEmptyWindowAt(e.getX(),e.getY());
      container.swapChildren(i,DragUtil.getComponent());
      e.setDropCompleted(true);
      e.consume();
    }
  }
);
  rt.widthProperty().addListener((o,ov,nv) -> {
    resizing=true;
    windows.forEach((i,w) -> {
      boolean s=w.snappable.get();
      w.snappable.unbind();
      w.snappable.set(false);
      double wx=container.properties.getD(i + "String_Node_Str");
      double ww=container.properties.getD(i + "String_Node_Str");
      if (container.properties.containsKey(i + "String_Node_Str"))       w.x.set(wx * nv.doubleValue());
      if (container.properties.containsKey(i + "String_Node_Str"))       w.w.set((ww - wx) * nv.doubleValue());
      maintain(GUI.snapping,w.snappable);
    }
);
    resizing=false;
  }
);
  rt.heightProperty().addListener((o,ov,nv) -> {
    resizing=true;
    windows.forEach((i,w) -> {
      boolean s=w.snappable.get();
      w.snappable.unbind();
      w.snappable.set(false);
      double wy=container.properties.getD(i + "String_Node_Str");
      double wh=container.properties.getD(i + "String_Node_Str");
      if (container.properties.containsKey(i + "String_Node_Str"))       w.y.set(wy * nv.doubleValue());
      if (container.properties.containsKey(i + "String_Node_Str"))       w.h.set((wh - wy) * nv.doubleValue());
      maintain(GUI.snapping,w.snappable);
    }
);
    resizing=false;
  }
);
}

Fixed version (ground truth):
public FreeFormArea(FreeFormContainer con){
  super(con);
  root.getChildren().add(rt);
  setAnchors(rt,0d);
  BooleanProperty isHere=new SimpleBooleanProperty(false);
  rt.setOnMousePressed(e -> isHere.set(isHere(e)));
  rt.setOnMouseClicked(e -> {
    if (!isAltCon && (GUI.isLayoutMode() || !container.lockedUnder.get())) {
      isHere.set(isHere.get() && isHere(e));
      if (e.getButton() == PRIMARY && isHere.get()) {
        addEmptyWindowAt(e.getX(),e.getY());
        e.consume();
      }
      if (e.getButton() == SECONDARY && container.getChildren().isEmpty()) {
        container.close();
        e.consume();
      }
    }
  }
);
  rt.setOnDragDetected(null);
  rt.setOnDragDone(e -> rt.pseudoClassStateChanged(DRAGGED_PSEUDOCLASS,false));
  rt.setOnDragOver(DragUtil.componentDragAcceptHandler);
  rt.setOnDragDropped(e -> {
    if (DragUtil.hasComponent()) {
      int i=addEmptyWindowAt(e.getX(),e.getY());
      container.swapChildren(i,DragUtil.getComponent());
      e.setDropCompleted(true);
      e.consume();
    }
  }
);
  rt.widthProperty().addListener((o,ov,nv) -> {
    resizing=true;
    windows.forEach((i,w) -> {
      boolean s=w.snappable.get();
      w.snappable.unbind();
      w.snappable.set(false);
      double wx=container.properties.getD(i + "String_Node_Str");
      double ww=container.properties.getD(i + "String_Node_Str");
      if (container.properties.containsKey(i + "String_Node_Str"))       w.x.set(wx * nv.doubleValue());
      if (container.properties.containsKey(i + "String_Node_Str"))       w.w.set((ww - wx) * nv.doubleValue());
      maintain(GUI.snapping,w.snappable);
    }
);
    resizing=false;
  }
);
  rt.heightProperty().addListener((o,ov,nv) -> {
    resizing=true;
    windows.forEach((i,w) -> {
      boolean s=w.snappable.get();
      w.snappable.unbind();
      w.snappable.set(false);
      double wy=container.properties.getD(i + "String_Node_Str");
      double wh=container.properties.getD(i + "String_Node_Str");
      if (container.properties.containsKey(i + "String_Node_Str"))       w.y.set(wy * nv.doubleValue());
      if (container.properties.containsKey(i + "String_Node_Str"))       w.h.set((wh - wy) * nv.doubleValue());
      maintain(GUI.snapping,w.snappable);
    }
);
    resizing=false;
  }
);
}