IlegalStateException in com.sun.ui.glass.View and javafx application thread hangs

I have a swing app and tranistioning to JavaFX (probably irrelevant but for completeness and correct picture sake) through JFXPanel (one of the tab/app)

I noticed the hanging of that JavaFX app and then this stacktrace in log.

Kind of pointing to glass toolkit but I am new to JavaFX.

RenderJob.run: internal exception
java.lang.IllegalStateException: The view has already been closed
    at com.sun.glass.ui.View.checkNotClosed(View.java:404)
    at com.sun.glass.ui.View.unlock(View.java:746)
    at com.sun.glass.ui.Pen.end(Pen.java:36)
    at com.sun.javafx.tk.quantum.UploadingPainter.run(UploadingPainter.java:145)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:304)
    at com.sun.prism.render.RenderJob.run(RenderJob.java:37)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:108)
    at java.lang.Thread.run(Thread.java:744)


The above sounds fishy. Probably the hanging part sound fishy. I can see other abstract method close in View class and its implementation in WinView. But the FX Application Thread shouldn't hang, correct?

Can it be a bug in javafx?


Additional Information:
Platform.setImplicitExit(false) has been set so that JavaFX RunTime doesnt exit either when the last window is closed as suggested by javadocs.