Characterbody3d falling through floor under specific circumstances related to falling.

This option is the closest. Very briefly — the game physics engine is deterministic and does not always have time to process collisions if objects move quickly. Example — a bullet flies through glass. In one physical frame it is in front of the glass, in the next — behind it. The glass remains intact, which is impossible in reality. That’s why in such a case you need to use a beam (raycasts), not a physical body.

Therefore, the realization of real physics in the game engine is not a very good idea. Falsification is more useful — our way is deception.