I put a wall and make the player to throw items, the map is a heightmap, and when the item collides the wall fall into the ground and don’t collide, dissapear, the ground swallow it.
I will try havok maybe this issue is solved
A lot of things can be happening with your scene, objects falling through are an extremely common occurrence if they not properly configured. Anyways, it will be hard to tell without an reproduction. 
msfs1992.github.io
go near the table until the grenade over gets highlighted, pick with F, aim the wall and hold left mouse button for a second until grenade throw pose finish, leave lmb to throw
Closing this since you opened another topic with basically the same subject a day after. Please don’t do this.
Dynamic mesh for player having climb up problems over heightmap terrain - Questions - Babylon.js (babylonjs.com)