Unfortunately, all of the MASON programs appears to do it.
Here is a copy of sim.app.tutorial1and2.tutorial2.
Just so you can see that the code is as you have provided it.
Single step the image does not appear.
Run it appears, if I interrupt the run the image goes away.
If I stop the run it remains on screen.
I never noticed it before as I have not enlarged the display window in any of the MASON provided programs.
In the way that I have been doing with my own program.
Microsoft Windows 10 Pro Version 10.0.14393 Build 14393 X64
Eclipse IDE for Java Developers Version: Mars.2 Release (4.5.2)
MASON 19 with a few updated components; GridBounded, GridLines.
I have made sure that everything on this computer has been upgraded to the latest versions.
I am stumped for now.
In the future, I will make sure I keep the frame size matching the display size and pretend it is not there
Thanks for all of your help.