Algodoo

That odd shaped object has a very low center of mass, which is along the bottom edge of the larger shaped portion, and that's why it behaves oddly.

But why is its center of mass.. There. Given the actual concentration of the matter, it should be fine.

Looks like the shape has the majority of it's weight at the left side. Even if the simulation is paused the shape can be imagined to fall like that.

wow. it just hangs out on the edge of the box! that's crazy!
But there are WAY more irratating bugs than that!

Ive noticed that fiked objects move, witch in my opinion, is dumb.

Question: "But why is its center of mass.. There. Given the actual concentration of the matter, it should be fine."

Answer: Because objects in Algodoo are not real. Therefore they do not actually have real mass. I don't know how you made that oddly-shaped object, but I do know that Algodoo objects can be made to twist and turn inside-out which can distribute the object's mass in very odd ways. It's just an artifact of a simulation which is not a perfect representation of real life objects. That's the best I can say about it. maybe someone else who is smarter than I am will come along and give a better explanation of this.

Heh, I figured that. I made it by starting the right shape (from the intersection point), then once i looped around (clockwise) I did the top shape (counterclockwise) and when i reached the bottom I did the bottom shape clockwise again.