Wide Intermediate Progress Bars do not "stop" in the center

[Exopandora]

Issue:
Wide Intermediate Progress Bars do not "stop" in the center of the Progress Bar. For small Progress Bars it works fine but the wider it becomes the more the center of the "stop" shifts to the right.

Video:

progressbar.mp4

Example code:
TestProgressBar.java:

import com.pixelduke.control.skin.FXSkins;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class TestProgressBar extends Application {
	@Override
	public void start(Stage stage) throws Exception {
		FXMLLoader loader = new FXMLLoader(this.getClass().getResource("TestProgressBar.fxml"));
		loader.setController(this);
		Parent root = loader.load();
		Scene scene = new Scene(root);
		scene.getStylesheets().add(FXSkins.getStylesheetURL()); 
		stage.setScene(scene);
		stage.show();
	}
	
	public static void main(String[] args) {
		Application.launch(args);
	}
}

TestProgressBar.fxml:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.geometry.Insets?>
<?import javafx.scene.control.ProgressBar?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.StackPane?>
<?import javafx.scene.layout.VBox?>

<VBox xmlns="http://javafx.com/javafx/15.0.1" xmlns:fx="http://javafx.com/fxml/1">
   <children>
      <AnchorPane>
         <children>
            <StackPane style="-fx-background-color: lightgrey;" AnchorPane.leftAnchor="340.0" AnchorPane.rightAnchor="340.0">
               <children>
                  <ProgressBar maxWidth="-Infinity" minWidth="-Infinity" prefWidth="300.0">
                     <StackPane.margin>
                        <Insets bottom="10.0" left="10.0" right="10.0" top="10.0" />
                     </StackPane.margin>
                  </ProgressBar>
               </children>
            </StackPane>
         </children>
      </AnchorPane>
      <StackPane style="-fx-background-color: lightgrey;">
         <children>
            <ProgressBar prefWidth="1000.0">
               <StackPane.margin>
                  <Insets bottom="10.0" left="10.0" right="10.0" top="10.0" />
               </StackPane.margin>
            </ProgressBar>
         </children>
      </StackPane>
   </children>
</VBox>

[Exopandora]

Same applies for JMetro