Halo 2 LASO anyone?

i got through half the campaign on SLASO (solo legendary all skulls on) up until regret. well the menu warnings lied to me by saying if I start a new playlist and return to laso, i would lose my checkpoint but continue from my last completed mission… yea i’m all the way back at Cairo station for some reason… If anyone wanted the LASO achievement and is decent at the game send me a msg. (btw my mic isn’t currently working)