My LASO Save File got corrupted, was on the Nexus mission, please read I need help

So the achievement is at 70% complete, I was at the Nexus mission, when one were you enter the command spire after going to each of those 4 forerunner structures. My save file got corrupted and I cant even load it, progress was wiped and it says the save has 0% complete, 10 seconds played but in the menu it says Nexus. Anyways, is it possible to start a game on Easy and speedrun before the mission start, then go to the menu, switch to legendary and activate the skulls? Also another minor gripe, if you load a save file from the menu instead of clicking continue it puts you back to the beginning of the mission, i’ve loved the game, but this is becoming unbearable.

I got the same thing on my first playthrough on Heroic. Had to start a new game and running through on legendary now.