Swing frame that contains JFXPanel (the project is attached) is not shown stochastically (50%) probably due to the fonts loading problems:

"AWT-EventQueue-0"
at sun.font.CFontManager.loadNativeDirFonts(CFontManager.java)
at sun.font.CFontManager.registerFontsInDir(CFontManager.java:145)
at sun.font.SunFontManager$2.run(SunFontManager.java:426)
at java.security.AccessController.doPrivileged(AccessController.java)
at sun.font.SunFontManager.<init>(SunFontManager.java:377)
at sun.font.CFontManager.<init>(CFontManager.java:46)
at jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(NativeConstructorAccessorImpl.java)
at jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:455)
at java.lang.Class.newInstance(Class.java:565)
at sun.font.FontManagerFactory$1.run(FontManagerFactory.java:83)
at java.security.AccessController.doPrivileged(AccessController.java)
at sun.font.FontManagerFactory.getInstance(FontManagerFactory.java:74)
at sun.font.SunFontManager.getInstance(SunFontManager.java:251)
at sun.font.FontDesignMetrics.getMetrics(FontDesignMetrics.java:264)
at sun.swing.SwingUtilities2.getFontMetrics(SwingUtilities2.java:1055)
at javax.swing.JComponent.getFontMetrics(JComponent.java:1644)
at javax.swing.plaf.basic.BasicGraphicsUtils.getPreferredButtonSize(BasicGraphicsUtils.java:351)
at com.apple.laf.AquaButtonUI.getPreferredSize(AquaButtonUI.java:443)
at com.apple.laf.AquaButtonUI.getMinimumSize(AquaButtonUI.java:431)
at javax.swing.JComponent.getMinimumSize(JComponent.java:1758)
at javax.swing.BoxLayout.checkRequests(BoxLayout.java:478)
at javax.swing.BoxLayout.layoutContainer(BoxLayout.java:420)
at java.awt.Container.layout(Container.java:1533)
at java.awt.Container.doLayout(Container.java:1522)
at java.awt.Container.validateTree(Container.java:1718)
at java.awt.Container.validateTree(Container.java:1727)
at java.awt.Container.validateTree(Container.java:1727)
at java.awt.Container.validateTree(Container.java:1727)
at java.awt.Container.validate(Container.java:1653)
at java.awt.Container.validateUnconditionally(Container.java:1690)
at java.awt.Window.show(Window.java:1032)
at java.awt.Component.show(Component.java:1693)
at java.awt.Component.setVisible(Component.java:1640)
at java.awt.Window.setVisible(Window.java:1013)
at app.App.<init>(App.java:144)
at app.App$7.run(App.java:221)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:759)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:712)
at java.awt.EventQueue$3.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(AccessController.java)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:77)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:729)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:199)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
"AWT-Shutdown"
at java.lang.Object.wait(Object.java)
at java.lang.Object.wait(Object.java:516)
at sun.awt.AWTAutoShutdown.run(AWTAutoShutdown.java:291)
at java.lang.Thread.run(Thread.java:843)
"Common-Cleaner"
at java.lang.Object.wait(Object.java)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
at jdk.internal.ref.CleanerImpl.run(CleanerImpl.java:148)
at java.lang.Thread.run(Thread.java:843)
at jdk.internal.misc.InnocuousThread.run(InnocuousThread.java:122)
"Finalizer"
at java.lang.Object.wait(Object.java)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:172)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216)
"FX Access Thread (Visual Debugger)"
at java.lang.Thread.sleep(Thread.java)
at org.netbeans.modules.debugger.jpda.visual.remote.RemoteFXService$FXAccessLoop.run(RemoteFXService.java:133)
"InvokeLaterDispatcher"
at java.lang.Object.wait(Object.java)
at java.lang.Object.wait(Object.java:516)
at com.sun.glass.ui.InvokeLaterDispatcher.run(InvokeLaterDispatcher.java:127)at java.lang.Thread.run(Thread.java:843)
"Java2D Disposer"
at java.lang.Object.wait(Object.java)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:172)
at sun.java2d.Disposer.run(Disposer.java:144)
at java.lang.Thread.run(Thread.java:843)
"Java2D Queue Flusher"
at java.lang.Object.wait(Object.java)
at sun.java2d.opengl.OGLRenderQueue$QueueFlusher.run(OGLRenderQueue.java:205)
at java.lang.Thread.run(Thread.java:843)
"JavaFX Application Thread"
at com.sun.javafx.font.coretext.OS.CTFontManagerRegisterFontsForURL(OS.java)
at com.sun.javafx.font.coretext.CTFontFile.registerFont(CTFontFile.java:58)
at com.sun.javafx.font.coretext.CTFactory.registerEmbeddedFont(CTFactory.java:56)
at com.sun.javafx.font.PrismFontFactory.populateFontFileNameMapGeneric(PrismFontFactory.java:1933)
at com.sun.javafx.font.PrismFontFactory.getFullNameToFileMap(PrismFontFactory.java:1835)
at com.sun.javafx.font.PrismFontFactory.getFontResource(PrismFontFactory.java:494)
at com.sun.javafx.font.LogicalFont.getSlot0Resource(LogicalFont.java:194)
at com.sun.javafx.font.LogicalFont.getDefaultAAMode(LogicalFont.java:409)
at com.sun.javafx.font.LogicalFont.getStrike(LogicalFont.java:413)
at com.sun.javafx.font.PrismFont.getStrike(PrismFont.java:73)
at com.sun.javafx.text.PrismTextLayout.setContent(PrismTextLayout.java:137)
at javafx.scene.text.Text.getTextLayout(Text.java:278)
at javafx.scene.text.Text.needsFullTextLayout(Text.java:233)
at javafx.scene.text.Text.access$900(Text.java:104)
at javafx.scene.text.Text$3.invalidated(Text.java:438)
at javafx.beans.property.StringPropertyBase.markInvalid(StringPropertyBase.java:110)
at javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:145)
at javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:50)
at javafx.scene.text.Text.setText(Text.java:419)
at com.sun.javafx.scene.control.skin.Utils.computeTruncationIndex(Utils.java:150)
at com.sun.javafx.scene.control.skin.Utils.computeClippedText(Utils.java:232)
at javafx.scene.control.skin.LabeledSkinBase.updateDisplayedText(LabeledSkinBase.java:1095)
at javafx.scene.control.skin.LabeledSkinBase.layoutLabelInArea(LabeledSkinBase.java:505)
at javafx.scene.control.skin.LabeledSkinBase.layoutLabelInArea(LabeledSkinBase.java:430)
at javafx.scene.control.skin.LabeledSkinBase.layoutChildren(LabeledSkinBase.java:414)
at javafx.scene.control.Control.layoutChildren(Control.java:599)
at javafx.scene.Parent.layout(Parent.java:1222)
at javafx.scene.Parent.layout(Parent.java:1229)
at javafx.scene.Parent.layout(Parent.java:1229)
at javafx.scene.Scene.doLayoutPass(Scene.java:585)
at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2501)
at com.sun.javafx.tk.Toolkit.lambda$runPulse$3(Toolkit.java:366)
at com.sun.javafx.tk.Toolkit$$Lambda$467.814296929.run
at java.security.AccessController.doPrivileged(AccessController.java)
at com.sun.javafx.tk.Toolkit.runPulse(Toolkit.java:365)
at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:392)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:510)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:490)
at com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit$11(QuantumToolkit.java:319)
at com.sun.javafx.tk.quantum.QuantumToolkit$$Lambda$112.1923707970.run
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
"Prism Font Disposer"
at java.lang.Object.wait(Object.java)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:172)
at com.sun.javafx.font.Disposer.run(Disposer.java:93)
at java.lang.Thread.run(Thread.java:843)
"QuantumRenderer-0"
at jdk.internal.misc.Unsafe.park(Unsafe.java)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:192)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2062)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1086)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1146)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:125)
at java.lang.Thread.run(Thread.java:843)
"Reference Handler"
at java.lang.Object.wait(Object.java)
at java.lang.Object.wait(Object.java:516)
at java.lang.ref.Reference.tryHandlePending(Reference.java:193)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:155)