ADDITIONAL SYSTEM INFORMATION :
Tested on Windows 10 with Java 10 and Java 12.
Bug occurs on JavaFX 10, 11, 13 (other versions not tested)

A DESCRIPTION OF THE PROBLEM :
When setStopTime is used on MediaPlayer, some medias plays about half as many times as is specified by setCycleCount.

So if I use player.setCycleCount(10), the sound plays only about 5 times instead of 10.

I did more tests and it seems that after playing once, currentCount is increased by 2 instead of 1, and OnEndOfMedia is triggered twice too.

The problem seems to be limited to some of the medias. An example is the file https://ia601701.us.archive.org/21/items/Laser_201304/laser.mp3 (about 1.8 seconds long)

The problem disappear if I stop using setStopTime.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Run the source code
2. Count the number of times the laser sound is played.
3. Look at the console output.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The laser sound is played 10 times, and each time it plays a single line is printed to the console.
ACTUAL -
The sound is played 5-8 times instead of 10.
On some plays, two lines are printed instead of one.

Example of output:

Current Count: 1 Seconds: 3.456
Current Count: 2 Seconds: 3.465
Current Count: 3 Seconds: 5.334
Current Count: 4 Seconds: 7.177
Current Count: 5 Seconds: 7.185
Current Count: 6 Seconds: 9.056
Current Count: 7 Seconds: 10.896
Current Count: 8 Seconds: 10.906
Current Count: 9 Seconds: 12.776
Current Count: 10 Seconds: 12.798

---------- BEGIN SOURCE ----------
package main;

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.media.Media;
import javafx.scene.media.MediaPlayer;
import javafx.scene.media.MediaView;
import javafx.stage.Stage;
import javafx.util.Duration;

public class Main extends Application {
    @Override
    public void start(Stage primaryStage) {
        Media media = new Media("https://ia601701.us.archive.org/21/items/Laser_201304/laser.mp3"); // replace this with your own audio file
        MediaPlayer player = new MediaPlayer(media);

        // Add to scene
        Group root = new Group(new MediaView(player));
        Scene scene = new Scene(root, 500, 200);

        // Show the stage
        primaryStage.setTitle("Media Player");
        primaryStage.setScene(scene);
        primaryStage.show();

        player.setCycleCount(10); // should run 10 times, but runs 5-8 times
        player.setStopTime(new Duration(1800)); // removing this fixes the issue

        long start = System.currentTimeMillis();
        player.setOnEndOfMedia(
                new Runnable() {
                    @Override
                    public void run() {
                        float sec = (System.currentTimeMillis() - start) / 1000F;
                        System.out.println("Current Count: " + player.getCurrentCount() + " Seconds: " + sec);
                    }
                });
        player.play();
    }
    public static void main(String[] args) {
        launch(args);
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Removing the line "player.setStopTime(new Duration(1800));" fixes the issue.

FREQUENCY : always