Problem Description:
On doing multiple drag and drop it ends up with Exception:
Exception in thread "JavaFX Application Thread" java.lang.IllegalStateException: Cannot start drag and drop outside of DRAG_DETECTED event handler

If we do some action after the initial exception more exception are coming.
Exception in thread "AWT-EventQueue-0" java.awt.dnd.InvalidDnDOperationException: Drag and drop in progress

Exception in thread "JavaFX Application Thread" drag recognized...java.lang.IllegalArgumentException: Key already associated with a running event loop: javafx.embed.swing.FXDnD@e4f5588

Steps to reproduce:
Run the attached test case SwingFXDnDTest.java
Do multiple drag and drop as shown in the attached video:drag_and_drop.mp4

Issue is reproducible in JDK8, JDK9 build 181 , JDK10 build 24.

There are small difference in the exception stack trace in JDK8 and 9(9 and 10 is same). So attached the stack trace for JDK 8 and 9.