Some objects falls through Plane with mesh collider(grenade)


I am learning Unity using a VTC course. I am at a part where i through grenades, but if my floor is a plane, then the grenades are falling through even with very slow speed settings. (grenades are generated by Insantiate and thrown from the character controller by a javascript)
The character, turret does not fall through the plane, nor the grenade as a normal gameobject placed on the ground.

I was under the impression a plane with mesh collider means nothing gets through it. It seems to behave like a strange grid regarding thrown grenades.
Is there any way to make the grid more dense so nothing false through it?

If i create a Cube and make it a plain plane like object, the grenade does not fall through. However I suspect the plane object does exist because cube is not intended to be used as a plane.

If i set the plain as convex the grenade does not fall through, however levitates as the convex option gives the mesh a very big and thick collider box.

I could live with convex ticked in but where I can set the size of it to perfectly fit the actual plain so no levitating objects above ground can be seen?

Thank you very much for the help in advance.

I don’t understand why the collisions aren’t working for you, however when I was working with thrown objects in my game ie glowstick, flare… the colliders were a bit too small so that if thrown even with small force it would fall though non-thick colliders so I made the collier on the thrown objects larger and with this made the rigid body “continuos dynamic”.

I still have this problem slightly when you pick up the object with a pickup script but maybe because the collider is thin thats why, maybe the falling or pushing of the object jerks its way through because it goes past the collider in the next frame making the editor think it just never actually touched it, so in simple you may have to work with a thicker collider or you could put a thicker collider on the thrown object. It seems that if you have absolute amazing fps it’ll be fine else, it may jerk its way through.

Simply make the Rigidbody collision detection = Continuous

I had the same problem but now it works fine.