JavaFX graphics bug with ProgressBar and slider

I am writing a small application (audio player with function);

This is the code of fxml:

<StackPane layoutY="64.0" prefHeight="20.0" prefWidth="492.0" AnchorPane.leftAnchor="26.0"     AnchorPane.rightAnchor="24.0">
  <children>
<ProgressBar id="progress" fx:id="progressBar" cache="true" cacheHint="QUALITY" disable="true" maxHeight="-1.0" maxWidth="1.7976931348623157E308" minHeight="-Infinity" minWidth="-Infinity" opacity="1.0" prefHeight="9.0" prefWidth="-1.0" progress="0.0" />
<Slider fx:id="progressSlider" disable="false" opacity="1.0" value="0.0" />
  </children>
</StackPane>

When the new track covers the old figure, it disappears

Who can help me?

Solution

I solved the problem I had to call the new JavaFX thread from the JavaFX thread;

Platform.runLater(new Runnable(){......});