Intermittent collision problems

I have a thin static mesh representing a playing card that I created in blender. I watched all videos on getting collisions to work and the mesh would fall through the floor when I turned on gravity and simulate physics. The interesting part is that a standard cube did not fall through the floor using similar settings. More interesting is that the same static mesh card does not fall through the cube. Still more interesting is if the card bounces off the cube and lands on the floor it does not fall through, unless it does a complete flip and then it does. i.e. it seems like one side of the card does not generate overlap with the floor but does with the cube. However, the floor does stop the card the first time I run the code after starting UE5, but not on subsequent runs.
Any ideas?

Substepping, or make the collision a laSubstring.
Or Probably both.

Set the collision to 1cm in thickness and start it off at the back of the card.

It won’t be perfect. If your game had falling cards as a feature you should rethink the approach.

Make the card into a blueprint.
Add 2 collision boxes.
Determine the way the card is facing when it’s close to hitting something and activate the proper collision box.

Or, alter the thickness of the collision by the card’s falling speed * some other parameter that increases it by an amount large enough to prevent penetration due to frame count issues / physics.

The engine in default settings should be able to handle collisions of 5mm.

However this may not be a good solution if you also expect good dynamic shadows on the table - hence the other options.

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Substepping did the trick for me so far. Thanks