Physics behave strangely, center of gravity doesn't seems to be right.

OS: win 10
Game Version: v0.60.0-6437
I made a stuff in 0.45 like this.
One ballast and one metal plate.
Anything work well in 0.45.

I have difficulty uploading images and files. So I decide to divide this thread into some floors. I will describe the problem in the following floors.
Then I deleted the metal plate. I thought that the left side lost some weight and it should slope to the right faster. Again in 0.60, but this time it slope to the left.