To reproduce:
1) open and run the attached NB project (it expects a JDK1.8 platform)
2) click on "Open…" button
3) select the attached FXML file (IssueTrackingLite.fxml)
4) move button "New" between "Save" and "Delete"
    => the exception below is raised and gesture is not performed

java.lang.IllegalArgumentException: failed to parse:scene.builder.internal
at java.awt.datatransfer.DataFlavor.<init>(DataFlavor.java:488)
at
javafx.embed.swing.SwingDnD$DnDTransferable.getTransferDataFlavors(SwingDnD.java:398)
at
sun.awt.datatransfer.DataTransferer.getFormatsForTransferable(DataTransferer.java:655)
at
sun.awt.dnd.SunDragSourceContextPeer.startDrag(SunDragSourceContextPeer.java:131)
at
sun.lwawt.macosx.CDragSourceContextPeer.startDrag(CDragSourceContextPeer.java:88)
at java.awt.dnd.DragSource.startDrag(DragSource.java:321)
at java.awt.dnd.DragSource.startDrag(DragSource.java:426)
at java.awt.dnd.DragGestureEvent.startDrag(DragGestureEvent.java:237)
at javafx.embed.swing.SwingDnD.startDrag(SwingDnD.java:284)
at javafx.embed.swing.SwingDnD.access$1000(SwingDnD.java:73)
at javafx.embed.swing.SwingDnD$4$1.run(SwingDnD.java:249)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:744)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at
java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:714)
at
org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:159)
[catch] at
java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at
java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)