ADDITIONAL SYSTEM INFORMATION :
Linux, Windows, Java 8u20+

A DESCRIPTION OF THE PROBLEM :
See this issue for reference:
https://bugs.openjdk.org/browse/JDK-8094371

The bug above was fixed in 8u20, but only for the default anchor location of WINDOW_TOP_LEFT (or other *TOP* anchor locations).

The bug above still exists, with no known workaround, for the anchor location of WINDOW_BOTTOM_LEFT or any *BOTTOM* location.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Here is a minimal reproducible example, copied from closed bug JDK-8094371, but setting the anchor location to WINDOW_BOTTOM_LEFT.

Drag the window to the right side of your screen, such that the tool-tip auto-fix behavior is used to adjust the position. Then notice that the tool-tip quickly hides after showing itself, and cycles hiding and showing (on Windows), or remains hidden (in my Linux environment).

Alternatively, set the anchor location to WINDOW_BOTTOM_RIGHT and note that the bad behavior exists regardless of whether you're near the edge of the screen! The tool-tip will show/hide/show/hide in a loop regardless of owner location.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The tool-tip should remain showing for the configured visible duration, instead of hiding immediately.
To accomplish this, the tool-tip must not steel focus from its owner, simply because of the configured anchor location and/or auto-fix setting.
ACTUAL -
The tool-tip steels the hover event from the owner node, causing it to hide itself.

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Tooltip;
import javafx.scene.layout.BorderPane;
import javafx.stage.PopupWindow.AnchorLocation;
import javafx.stage.Stage;

public class ToolTipIssue extends Application {

   // boilerplate to build a button, add it to a stage, and show stage
   public static void main(String[] args) {
      launch(args);
   }

   @Override
   public void start(Stage primaryStage) {
      BorderPane root = new BorderPane();
      Button button = new Button();
      BorderPane.setAlignment(button, Pos.CENTER_RIGHT);
      button.textProperty().bind(Bindings.when(button.hoverProperty()).then("HOVERED Button")
            .otherwise("Regular Button"));
      Tooltip tip = new Tooltip("I am a button's tooltip.");
      tip.setAnchorLocation(AnchorLocation.WINDOW_BOTTOM_LEFT);
      button.setTooltip(tip);
      root.setRight(button);
      primaryStage.setScene(new Scene(root, 450, 150));
      primaryStage.show();
   }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
No known workaround if the user desires a tool-tip anchor location of WINDOW_BOTTOM_LEFT or WINDOW_BOTTOM_RIGHT. The only workaround is to use the default anchor location of WINDOW_TOP_LEFT or WINDOW_TOP_RIGHT, neither of which may be desirable depending on client needs.

FREQUENCY : always

edit 2023/09/05: on Mac, the tooltip shows and hides itself, then remains hidden.