Falling through the ground isn’t necessarily the collider itself, but rather that it’s a dynamic object. I see this happen in my game too with dynamic objects that the player interacts with or carries. One thing I do is slow down the movement of the objects in question.
Also in Project Settings you can tweak some settings to improve how physics is detecting moving objects more frequently.
Project Settings → Physics → Substepping on.
I also play with the Max Substeps. I think the default is 6 and you can increase it, but it isn’t without paying a price on the game engine.
In one part of my game I teleport objects that can be thrown off of high areas in my game. If those objects fall and are important they teleport back into the game to a spot where I make sure they hit at least one thing on the way down (they pick up speed as they fall after all ) and then they hit the surface I want them on slowed down. Because objects like this are important in my game, and they are limited I’m using this solution over increasing Physics calculations. I put my trigger volume under my world where things may vanish through the floor, and they come back.
i know it’s not ideal, but I spend about fifty percent of my game development time lately trying to keep my game running at a decent frame rate… so anything I can do to eliminate slow downs is important.