You're definitely right about the memory leak - thanks for the catch! Will fix that shortly. I'll try to see if I can think up a simple scenario also which would cause this problem to happen. It was definitely happening for us when changing scene in response to button clicks (detected by the debug checking function above) so it should be reproducible on some smaller scale too. We added the debug checks in this pull request because we were occasionally getting crashes in event handling code (typically after button clicks) which was being caused by sending events to deleted objects. The assertions helped us detect these erroneous conditions and let us know that our fix was working and that no events could be sent to deleted objects.