Another Inverted Mask Issue

[Willyboo]

Hey there. I've been surfing about the internet looking for a solution. Perhaps you folks can help me?

I'm sure you've seen this problem before: Someone wants to use a mask inversely, hiding the masked object instead of revealing it. The only coded solution is to create a bigger "stage" mask with the inverse mask cut out. I understand the process, and have a slight grip on methods of executing it.

Too bad it still will not work properly.

In the attachment below I am employing a solution used here: Not actually where I got the code, but this was the same code my source employed.

And where it works for some people, it is not working in my instance. If you look at my files, the masks cut out rather strangely. Is there something different about this situation that requires a different line of code, or am I simply using it wrong?

Because the object will be squishing and changing shape, creating the mask frame by frame would be a hassle. Changing the shape of a solid mask is a lot easier than moving the particular points of a "stage" mask manually.