This isn't a bug.
When you use apply the physics behaviour to an object, any other motion you give it directly conflicts with the physics. You're basically telling C2 "this object is bound by the laws of physics", and also "spin this object because I said so" - which are conflicting messages.
First, you should use the "apply torque" action to rotate your lab instead of simply rotating the sprite. But this requires that you set immovable to no, which is obviously a bit of an issue because the lab would collapse to the ground. I'd suggest that you create a new, invisible or visible, non-collidable object (a "pin" so to speak) and bind the lab to that with a revolute joint. Set the pin to be immovable, effectively trapping the lab in place but allowing it to rotate freely.
You should also alter the density of your sand and lab objects to better represent their approximate mass in the real world (so the sand doesn't "push" around the lab).Here's an updated capx for you