Bryan Atsatt:

I'm nearly certain I found a bug in NashornScriptEngine.invokeImpl():
    self = ScriptObjectMirror.unwrap(self, ctxtGlobal);
should be:
    self = ScriptObjectMirror.unwrap(self, oldGlobal);
When I re-build with this fix, my new multi-threaded version of node.jar works correctly. Without it, the unwrap fails when the global is not the context global.