ADDITIONAL SYSTEM INFORMATION :
Any system, latest JFX 15 or 16

A DESCRIPTION OF THE PROBLEM :
String representation of javafx.scene.input.PickResult always gives incorrect result, because it lacks one closing square bracket(']') in the end of method.

I found this bug implementing beautify(String) method, that was "moving" every new javafx.scene.input.MouseEvent on tab further. I couldn't find bug in my code, so i just counted amount of opening and closing square brackets: number of opening was one more than closing. I digged in source code of toString and MouseEvent's toString() looked ok to me, so i noticed that problem might be in PickResult.toString(). So there was. Comparison of toString methods and place of bug:
https://prnt.sc/10rh7dp
https://prnt.sc/10rh8bh

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Create new JavaFx application, add MouseEvent handler to pane/scene and print it when MouseEvent occurs.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
  beautified:
  MouseEvent [
      source = javafx.scene.Scene@1fb3f629,
      target = Rectangle[
          x=0.0,
          y=0.0,
          width=101.0,
          height=101.0,
          fill=0x808080ff
      ],
      eventType = MOUSE_MOVED,
      consumed = false,
      x = 1203.0,
      y = 474.0,
      z = 0.0,
      button = NONE,
      pickResult = PickResult [
          node = Rectangle[
              x=0.0,
              y=0.0,
              width=101.0,
              height=101.0,
              fill=0x808080ff
          ],
          point = Point3D [
              x = 84.0,
              y = 38.0,
              z = 0.0
          ],
          distance = 2644.1579971625497
      ]
  ]
plain text:
MouseEvent [source = javafx.scene.Scene@874f0c1, target = Rectangle[x=0.0, y=0.0, width=101.0, height=101.0, fill=0x808080ff], eventType = MOUSE_MOVED, consumed = false, x = 1425.0, y = 358.0, z = 0.0, button = NONE, pickResult = PickResult [node = Rectangle[x=0.0, y=0.0, width=101.0, height=101.0, fill=0x808080ff], point = Point3D [x = 84.0, y = 33.0, z = 0.0], distance = 2644.1579971625497]]

ACTUAL -
  beautified:
  MouseEvent [
      source = javafx.scene.Scene@1fb3f629,
      target = Rectangle[
          x=0.0,
          y=0.0,
          width=101.0,
          height=101.0,
          fill=0x808080ff
      ],
      eventType = MOUSE_MOVED,
      consumed = false,
      x = 1203.0,
      y = 474.0,
      z = 0.0,
      button = NONE,
      pickResult = PickResult [
          node = Rectangle[
              x=0.0,
              y=0.0,
              width=101.0,
              height=101.0,
              fill=0x808080ff
          ],
          point = Point3D [
              x = 84.0,
              y = 38.0,
              z = 0.0
          ],
          distance = 2644.1579971625497
      ]
plain text:
MouseEvent [source = javafx.scene.Scene@874f0c1, target = Rectangle[x=0.0, y=0.0, width=101.0, height=101.0, fill=0x808080ff], eventType = MOUSE_MOVED, consumed = false, x = 1425.0, y = 358.0, z = 0.0, button = NONE, pickResult = PickResult [node = Rectangle[x=0.0, y=0.0, width=101.0, height=101.0, fill=0x808080ff], point = Point3D [x = 84.0, y = 33.0, z = 0.0], distance = 2644.1579971625497]

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import javafx.event.Event;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class App extends Application {

    @Override
    public void start(Stage stage) {
        var javaVersion = SystemInfo.javaVersion();
        var javafxVersion = SystemInfo.javafxVersion();

        var label = new Label("Hello, JavaFX " + javafxVersion + ", running on Java " + javaVersion + ".");
        var pane = new StackPane(label);
        
        pane.addEventHandler(MouseEvent.ANY, this::handleMouse);
        
        var scene = new Scene(pane, 640, 480);
        stage.setScene(scene);
        stage.show();
    }

    private void handleMouse(MouseEvent t){
        System.out.println(beautify(t.toString()));
        //notice there is no closing bracket with zero tabs, that's the problem
        System.out.println();
        System.out.println(t.toString());
        System.exit(0);
    }
    public static String beautify(String startingString){
        final int tabLength = 4;
        int tabs = 0;
        StringBuilder sb = new StringBuilder(startingString.length());
        sb.append('\n');

        for(int i = 0; i < startingString.length(); i++){
            char c = startingString.charAt(i);
            if(c == '{' || c == '['){
                tabs++;
                sb.append(c);
                sb.append('\n');
                sb.append(" ".repeat(tabs*tabLength));
            }else if(c == '}' || c == ']'){
                tabs--;
                sb.append('\n');
                sb.append(" ".repeat(tabs*tabLength));
                sb.append(c);
            }else if(c == ','){
                sb.append(c);
                sb.append('\n');
                sb.append(" ".repeat(tabs*tabLength -1));
            }else
                sb.append(c);
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        launch();
    }

}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
just add .append(']') in the end of PickResult.toString() method.

FREQUENCY : always