ADDITIONAL SYSTEM INFORMATION :
I don't understand why JDK 9 is not on the list of versions for this report, because that's the one I am using to develop. If the question is which runtime java version I am executing the app with, how would I find that out in IntelliJ with a Gradle-based project?

A DESCRIPTION OF THE PROBLEM :
In my app I consistently get this exception when I try to drag certain things from external applications over rows in a TreeTableView.

Unfortunately, the code is private, but let me know if there is any additional information I can provide.


When I did a search for this issue I interestingly found someone else with a similar issue:
https://github.com/defold/editor2-issues/issues/1791

The exception is thrown in a thread I don't control so until I start taking things apart I don't know exactly what in my code causes it:

THREAD=Thread[JavaFX Application Thread,5,system]
THROWABLE: java.lang.UnsupportedOperationException: Flush is forbidden from target!
CLASS=class java.lang.UnsupportedOperationException
MESSAGE=Flush is forbidden from target!
javafx.graphics/com.sun.glass.ui.View$2.flush(View.java:1022)
javafx.graphics/com.sun.javafx.tk.quantum.QuantumClipboard.flush(QuantumClipboard.java:274)
javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.startDrag(QuantumToolkit.java:1232)
javafx.graphics/javafx.scene.Scene$DnDGesture.dragDetectedProcessed(Scene.java:3072)
javafx.graphics/javafx.scene.Scene$DnDGesture.process(Scene.java:3141)
javafx.graphics/javafx.scene.Scene$DnDGesture.access$8400(Scene.java:3028)
javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3892)
javafx.graphics/javafx.scene.Scene$MouseHandler.access$1300(Scene.java:3604)
javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1874)
javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2613)
javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:397)
javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
java.base/java.security.AccessController.doPrivileged(Native Method)
javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:434)
javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:433)
javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:556)
javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:942)
javafx.graphics/com.sun.glass.ui.mac.MacView.notifyMouse(MacView.java:127)


REGRESSION : Last worked in version 10.0.2


FREQUENCY : often