I have a reproducible SIGSEGV in a project I am writing. The issues seems to boil down to having a Stage that contains a defaultbutton. The button has onAction handler, which in turn hides the Stage. JVM seems to crash consistently with this in the stack:

GtkView(View).notifyKey(int, int, char[], int) line: 951

There is no crash if the button is clicked using mouse, or if the Stage is not hidden from the onAction handler.

Educated guess: the key down event is generated from Gtk, handler is triggered and Stage is hidden, and when the key up event is generated, something goes wrong.