I guess this is realy easy, and im just missing something.

But I have particles emiting from a moving object, source from object.
Applied to the emittor is, gravity (force), drag, and collision.

The particles have Slide on Collision as behaviour, and they slide nice when they collide with the grid, and the drag slows them down so they dont spread out to much.

But after a couple of frames a random amount of particles which motion have stopped, starts to suddenly fall through the grid.

What am I missing ?

/M