As you can see in this video, the physics of the boxes do strange things in some situations (minute 0:18).
Can this be improved?
I don’t see the problem?
Maybe you can increase the Linear/Angular Damping of the Meshes if you want them to be “heavier” to move.
This is the setup of the physics and collision variables of the box (images attached)
My expectations are that the boxes have a real behavior to what could be a generic box of 20 kg.
In the video you see some strange movement during the tour and it looks strange.