So, just started playing this the other day. Learned the hard way why you should always "save and quit" instead of just powering down. In my haste to come up with some kind of fix, I started a new campaign from the mission I was on, to see if it would let me continue in the story. For some reason it won't, kicking me back to Mombosa Nights, giving me a bunch of objectives to "investigate what happened to ODST teammates" and such.
I've come to accept that I'm going to have to play through every Mission again to get a campaign complete achievement. However, since I completed most of the missions on Legendary already, is it possible to do a quick playthrough on Normal, and then re-do the ones I have left on Legendary to get the "Campaign Complete: Legendary" achievement? Or should I just continue from the save I currently have on Legendary, with only the Flying around the Subway mission finished? Or, even worse, should I just start a new save? Thanks