ahh i see. i will raise the ceiling by one tile soon. thx for info

Yeah, it's definitely a problem with the game engine, not your chamber.

The way it works is this: If you're on the platform beneath the cube dispenser, throw the cube into the goo below. When it's destroyed, the dispenser will drop another cube. As it does, look up and grab the cube just as it's coming out. You'll be holding the cube, but it will still be inside the dispenser. If you timed it right, the dispenser will get confused and drop a second cube, and now you have two cubes.

The problem comes from the fact that the platform is directly below the dispenser. If it were, say, two tiles' distance, you wouldn't be able to hold the cube inside the dispenser and the problem wouldn't occur. The only solution I can think of would be to raise the ceiling by one tile -- that is, if you even think it's a problem. Having two cubes doesn't break the level or anything. I'm not even sure it makes the level any easier. It's just an oddity that I noticed. :)

im not quite sure what you mean is problem with my chamber :) it sounds like some kind of thing that i cant fix...