Load the attached FXML file.
Select All and drop it from Content to Library ==> that creates an AnchorPane_1 row in Custom section.
Drag the AnchorPane_1 row from Library / Custom back to Content and drop it at some place the drop is accepted ==> the exception below is thrown.
The user doesn't see anything added to his layout but SceneBuilder remains fully usable.

Mar 13, 2014 4:07:43 PM com.oracle.javafx.scenebuilder.app.SceneBuilderApp$SceneBuilderUncaughtExceptionHandler uncaughtException
SEVERE: An exception was thrown:
java.lang.IllegalStateException: Bug in FXOMRefresher: FXML dumped in /tmp/DTL-5996-2316447409895190097.fxml
at com.oracle.javafx.scenebuilder.kit.fxom.FXOMRefresher.refresh(FXOMRefresher.java:84)
at com.oracle.javafx.scenebuilder.kit.fxom.FXOMDocument.refreshSceneGraph(FXOMDocument.java:275)
at com.oracle.javafx.scenebuilder.kit.fxom.FXOMDocument.endUpdate(FXOMDocument.java:262)
at com.oracle.javafx.scenebuilder.kit.editor.job.BatchJob.execute(BatchJob.java:125)
at com.oracle.javafx.scenebuilder.kit.editor.JobManager.executeJob(JobManager.java:191)
at com.oracle.javafx.scenebuilder.kit.editor.JobManager.push(JobManager.java:80)
at com.oracle.javafx.scenebuilder.kit.editor.drag.DragController.end(DragController.java:125)
at com.oracle.javafx.scenebuilder.kit.editor.panel.library.LibraryPanelController$8.handle(LibraryPanelController.java:668)
at com.oracle.javafx.scenebuilder.kit.editor.panel.library.LibraryPanelController$8.handle(LibraryPanelController.java:663)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:204)
at javafx.scene.Scene$DnDGesture.processDropEnd(Scene.java:3062)
at javafx.scene.Scene$DnDGesture.access$6800(Scene.java:2896)
at javafx.scene.Scene$DragSourceListener.dragDropEnd(Scene.java:3306)
at com.sun.javafx.tk.quantum.GlassScene$3$1.run(GlassScene.java:252)
at com.sun.javafx.tk.quantum.GlassScene$3$1.run(GlassScene.java:247)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassScene$3.actionPerformed(GlassScene.java:247)
at com.sun.glass.ui.Clipboard.actionPerformed(Clipboard.java:173)
at com.sun.glass.ui.gtk.GtkDnDClipboard.pushToSystem(GtkDnDClipboard.java:41)
at com.sun.glass.ui.SystemClipboard.flush(SystemClipboard.java:51)
at com.sun.glass.ui.ClipboardAssistance.flush(ClipboardAssistance.java:59)
at com.sun.javafx.tk.quantum.QuantumClipboard.flush(QuantumClipboard.java:274)
at com.sun.javafx.tk.quantum.QuantumToolkit.startDrag(QuantumToolkit.java:1150)
at javafx.scene.Scene$DnDGesture.dragDetectedProcessed(Scene.java:2940)
at javafx.scene.Scene$DnDGesture.process(Scene.java:3009)
at javafx.scene.Scene$DnDGesture.access$8400(Scene.java:2896)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3762)
at javafx.scene.Scene$MouseHandler.access$1800(Scene.java:3471)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1695)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2486)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:314)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:243)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:345)
at com.sun.glass.ui.View.handleMouseEvent(View.java:526)
at com.sun.glass.ui.View.notifyMouse(View.java:898)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.access$200(GtkApplication.java:48)
at com.sun.glass.ui.gtk.GtkApplication$6$1.run(GtkApplication.java:149)
at java.lang.Thread.run(Thread.java:744)
Caused by: java.io.IOException: javafx.fxml.LoadException: Value "txtDSCity" does not exist.
/home/javafx/Documents/toto.fxml:148

at com.oracle.javafx.scenebuilder.kit.fxom.FXOMLoader.load(FXOMLoader.java:92)
at com.oracle.javafx.scenebuilder.kit.fxom.FXOMDocument.<init>(FXOMDocument.java:80)
at com.oracle.javafx.scenebuilder.kit.fxom.FXOMRefresher.refresh(FXOMRefresher.java:60)
... 57 more
Caused by: javafx.fxml.LoadException: Value "txtDSCity" does not exist.
/home/javafx/Documents/toto.fxml:148

at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2613)
at javafx.fxml.FXMLLoader.access$100(FXMLLoader.java:104)
at javafx.fxml.FXMLLoader$ReferenceElement.constructValue(FXMLLoader.java:1200)
at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:740)
at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2723)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2527)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2425)
at com.oracle.javafx.scenebuilder.kit.fxom.FXOMLoader.load(FXOMLoader.java:89)
... 59 more