As I posted, shutting down JPanel windows under certain circumstances causes the X server to stay in an intermittent state. I have tried the following:

• Click the close box w/ window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) configured caused subsequent runs to create windows with partial functionality. (I have since changed to DO_NOTHING_ON_CLOSE.)
• Right-click on the X server (to enable the fluxbox menu) and exit was a disaster. No graphics worked after that (though I am not sure how to describe it exactly).
• Closing everything (Chrome, OS, etc.), clearing all browser data, and relogging into repl.it. This just puts me back into the https://RedCrossRedTargetAssignment.psb-david-petty.repl.run window unchanged.
• Waiting overnight seems to have 'reset' the X server (though, how long do users of repl.it Java Swing have to wait?).

I would really like to be able to shut down or restart the X server reliably (under control of the .replit file) from a Java Swing repl!