Staggering effect bug

If a player throws a grenade, and someone tries to block it, the throwing player gets the staggering effect, as if blocked. Same with placing a landmine. (Pretty well known, I suppose.)

If a player is blocking when the portcullis or sandworm kills him, then the player who last damaged the dying player gets the staggering effect.

I couldn't achieve similar effect with the spikes or the black hole.