We have a pretty complex application and currently migrating to 8u20. After some minutes of using the application following NullPointerException is thrown (it's not deterministically reproducible):

java.lang.NullPointerException
 at javafx.scene.Scene$ScenePulseListener.synchronizeSceneProperties(Scene.java:2308)
 at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2396)
 at com.sun.javafx.tk.Toolkit.lambda$runPulse$28(Toolkit.java:314)
 at com.sun.javafx.tk.Toolkit$$Lambda$119/91127710.run(Unknown Source)
 at java.security.AccessController.doPrivileged(Native Method)
 at com.sun.javafx.tk.Toolkit.runPulse(Toolkit.java:313)
 at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:340)
 at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:451)
 at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:431)
 at com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit$363(QuantumToolkit.java:298)
 at com.sun.javafx.tk.quantum.QuantumToolkit$$Lambda$42/1144661910.run(Unknown Source)
 at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
 at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
 at com.sun.glass.ui.win.WinApplication.lambda$null$141(WinApplication.java:102)
 at com.sun.glass.ui.win.WinApplication$$Lambda$38/1693608813.run(Unknown Source)
 at java.lang.Thread.run(Thread.java:745)

Unfortunately I don't think I can extract an example to reproduce this NPE.