BauSystem_Main/src/de/steamwar/bausystem/features/simulator2/gui/SimulatorGroupChooserGui.java

@@ -54,6 +54,7 @@ public class SimulatorGroupChooserGui extends SimulatorPageGui<SimulatorGroup> {
                 SimulatorGroup newParent = new SimulatorGroup();
                 newParent.add(subject);
                 simulator.getElements().add(newParent);
+                parent.getElements().remove(subject);
                 back.open();
                 SimulatorWatcher.update(simulator);
             }));