The problem in your Hit the Boxes game is not an engine issue but an issue in your game.
Simply set the collision shape to sphere or capsule and change the angular factor to 0.
Then everything should work without any shaking.
About your prefab issues: Can you please send me an example file that does not work?
I just fixed the position input issue. The input field was set to integer instead of float.
You will be able to grab it in one of the next daily builds.
Btw: Your game looks quite nice 😀