On this project, I noticed that, if you press the right arrow until you get to the Scratch Cat, and set the ghost effect up a bit, the overlapping vector objects are visible. Apply whirl effect and this disappears.

I have noticed this bug too. It needs to be fixed.

It isn't a bug. It's user error.

If you have something with 10% opacity on top of something else with 10% opacity it creates 20% opacity. Therefore not faded as quickly.