ADDITIONAL SYSTEM INFORMATION :
System with 2 displays (Display 1: 1920x1080 at 100% scaling, Display 2: 2560x1440 at 200% scaling)
Windows 10 Build 14393
OpenJDK 11.0.7+10.2 (LTS)

A DESCRIPTION OF THE PROBLEM :
Frames are not correctly positioned when the client machine running the VM has multiple displays at differing resolutions and scaling. This issue exists in these tested versions:
v11.0.7+10.2
v15-ea+29
v16-ea+3

This is regardless of which of the two displays is the main display and the orientation of the two displays to each other. If one display is at 100% scaling and the other display is at >100% scaling this problem occurs.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the sample code provided in the java.awt.GraphicsDevice class comment:

GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice[] gs = ge.getScreenDevices();
for (int j = 0; j < gs.length; j++) {
    GraphicsDevice gd = gs[j];
    GraphicsConfiguration[] gc =gd.getConfigurations();
    for (int i=0; i < gc.length; i++) {
       JFrame f = new JFrame(gs[j].getDefaultConfiguration());
       Canvas c = new Canvas(gc[i]);
       Rectangle gcBounds = gc[i].getBounds();
       int xoffs = gcBounds.x;
       int yoffs = gcBounds.y;
       f.getContentPane().add(c);
       f.setLocation((i*50)+xoffs, (i*60)+yoffs);
       f.show();
    }
 }

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Expected a frame to be created in the upper left corner of each display on the system.
ACTUAL -
Two frames appear on Screen Device #0 (one of these should have been the one positioned for Screen Device #1).

---------- BEGIN SOURCE ----------
import javax.swing.*;
import java.awt.*;

class Scratch {
    public static void main(String[] args) {
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice[] gs = ge.getScreenDevices();
        for (int j = 0; j < gs.length; j++) {
            GraphicsDevice gd = gs[j];
            GraphicsConfiguration[] gc = gd.getConfigurations();
            for (int i = 0; i < gc.length; i++) {
                JFrame f = new JFrame(String.format("Graphics Device #%d",j), gs[j].getDefaultConfiguration());
                Canvas c = new Canvas(gc[i]);
                Rectangle gcBounds = gc[i].getBounds();
                int xoffs = gcBounds.x;
                int yoffs = gcBounds.y;
                f.getContentPane().add(c);
                f.setLocation((i * 50) + xoffs, (i * 60) + yoffs);
                f.show();
            }
        }
    }
}
---------- END SOURCE ----------

FREQUENCY : always