here's scene >
https://www.sendspace.com/file/95e77oDescription:
Basic scene (cube, plane, sun, sky) with buggy settings.
After rendering for 2 min. one of cores stops rendering, rest of cores continue (75%).
Stoping only stops Rendering counter, yet cores are still used and continue calculating rays.
Closing Corona engine stops rendering, yet doesn't stop the process (still on in WinTaskManager - 0%).
ohsnapitjoel posted on BA forums the reason is using Progressive (renderer) with HD Cache (GI solver).
After testing other combinations (renderer+solver) proved there's bug, 'cuz they work without hanging.