Hey R0jo, I'm still battling that one issue I encountered earlier, and it is quite weird since it only happens in certain levels.
I have had some difficulty in pinpointing the problem, but now I will scrap rest of my game and try to gather just bare bones version for demonstrating the error.. it happens when you make joints between sprites, and then one sprite's frame has been changed on the fly and it undergoes several collisions. Attached below is what I get in the console:
Uncaught TypeError: Cannot read property 'parent' of undefined
.capx to be followed as soon as I manage to strip it =)