Tiberius

I've been playing through the Legendary campaigns in co-op with a friend of mine. In Halo 2, when one of us dies, we go back to the checkpoint, as if we have the Iron skull on. Is it supposed to be like this? Was it always like this? As a side note, we only had Sputnik, Grunt Birthday Party, Prophet Birthday Party, and IWHBYD on. One last thing: We finished Cairo Station and got the achievement for beating a level on Heroic or Legendary with the Masterblaster skull on, and we didn't have it on. Is the entire campaign glitched out? I know the game is having problems, but...wow...