[kunalb]

Just judging by the symptoms without looking at the code, I'd say that perhaps you're only animating the secondary rectangle that mimics the first one when the primary rectangle intersects with the wormhole's edge.

When we move the first rectangle too fast towards the top, some of the events might get missed and the corresponding rectangle doesn't _exactly_ mimic the first one. As no more events are fired, it gets stuck.

You might want to introduce some sort of sanity check for when a rectangle exits the wormhole.