To reproduce, run the attached test program on a Windows 10 system with the Windows 10 1709 (the Fall Creators update) with screen scale set to 125% or greater. It will fail to move the mouse to the correct location.

To compile it, you need the following flag:

javac --add-exports javafx.graphics/com.sun.glass.ui=ALL-UNNAMED SimpleFXRobotTest.java

Before you run it, move your mouse to a corner of the screen.

Note that at least one FX Robot-based test, TabPaneDragPolicyTest, also fails in the same way.

This seems to be a bug introduced by Microsoft in Windows 10 in the mouse_move function.

I note that AWT robot also fails similarly.