Run the current 6.0.9 build. Load any system for gaming, then open preferences and make changes. Push apply or ok buttons. The preferences will fail to save.
The root cause was continued small issues regarding the side by side running of javaFX and Swing. The workers crashed on illegal state exceptions.
Making changes required to allow the current gui to work, will have to be revisited as UI transition continues.
Linux, JDK 12
Fix merged, closing.
Just going through states.