Take the following javafx code:

Stage {
    title: "Radial Gradient CSS"
    scene: Scene {
        width: 250
        height: 80
        stylesheets: "{__DIR__}styles.css"
        content: [
            Rectangle {
                width: 200
                height: 80
            }
        ]
    }
}

with this stylesheet:

Rectangle {
    -fx-fill: linear (0%,0%) to (100%,100%) stops (0%, blue) (100%, red);

    -fx-fill: radial 100% stops (0%, blue) (100%, red);
    -fx-fill: radial (25%, 25%), 100% stops (0%, blue) (100%, red);
    -fx-fill: radial (25%,25%), 100% stops (0%, blue) (100%, red) reflect;
    -fx-fill: radial (25%,25%), 100% focus(25%,25%) stops (0%, blue) (100%, red);
}

The linear gradient works fine, but the four versions of the radial gradient does not. None of the four generates a parser error but the following exception is thrown in each case:

Unexpected exception caught in MasterTimer.timePulse():
java.lang.ClassCastException: javafx.scene.paint.CycleMethod cannot be cast to com.sun.stylesheet.css.Size
        at com.sun.stylesheet.css.Type$Type$Script$1Type$ObjLit$10.derive(Type.fx:160)
        at com.sun.stylesheet.css.Type$PaintType.getParsedValue(Type.fx:646)
        at com.sun.stylesheet.css.Type$PaintType.convert(Type.fx:635)
        at com.sun.stylesheet.css.Type.convert(Type.fx:211)
        at com.sun.stylesheet.StyleHelper.lookup(StyleHelper.fx:330)
        at com.sun.stylesheet.StyleHelper.transitionToState(StyleHelper.fx:168)
        at javafx.scene.Node.impl_processCSS(Node.fx:3107)
        at javafx.scene.Parent.impl_processCSS(Parent.fx:875)
        at javafx.scene.Scene.doCSSPass(Scene.fx:285)
        at javafx.scene.Scene$ScenePulseListener.pulse(Scene.fx:924)
        at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.fx:143)
        at com.sun.javafx.tk.Toolkit.handleMasterTimerPulse(Toolkit.fx:132)
        at com.sun.javafx.tk.Toolkit$1com$ObjLit$5.firePulseImpl(Toolkit.fx:304)
        at com.sun.scenario.ToolkitAccessor.firePulse(ToolkitAccessor.java:55)
        at com.sun.scenario.scenegraph.JSGPanelRepainter$FrameDisplay.run(JSGPanelRepainter.java:133)
        at com.sun.scenario.animation.AbstractMasterTimer.timePulseImpl(AbstractMasterTimer.java:420)
        at com.sun.scenario.animation.AbstractMasterTimer$MainLoop.run(AbstractMasterTimer.java:296)
        at com.sun.embeddedswing.EmbeddedEventQueue.doPulse(EmbeddedEventQueue.java:570)
        at com.sun.embeddedswing.EmbeddedEventQueue.access$000(EmbeddedEventQueue.java:82)
        at com.sun.embeddedswing.EmbeddedEventQueue$2.run(EmbeddedEventQueue.java:473)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:633)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)