I'm new to an approximately 50K-line Java project using JavaFX, and I'm getting a bug nobody else in the group seems to be able to duplicate. Unfortunately I can't share any code, so this is just a hope that this is a familiar issue to anyone else, or that there are suggestions about how to think about and solve this problem.
The application itself is a launcher with five different modes. The minimum working system requires running two different instances of the application and starting mode #1 in the first and mode #2 in the second. The two communicate with each other over IP.
Mode #1 works fine, stays open indefinitely; at any rate, I haven't been able to make it close unexpectedly. Mode #2 is the problem. After opening Mode #2, if I click on any other window, taking focus off of it, the window disappears within a second or two. I get no error message or any other symptom. The eclipse console just reads at the top. If I don't click elsewhere, it runs several minutes at least without comment.
I have no idea how to go about solving this problem. I can't seem to use a debugger because it doesn't seem to hold onto memory after crashing. There's nothing about crashing when the focus is taken off that matches up with any of my knowledge.
It's a simple window, two buttons, a menu, and an output text box.
With these clues, do you have any suggestions about how to proceed?