Checkpoints not saving in some missions

Hello everyone! I’m currently playing MCC on PC and having a blast. I’m going through Reach campaign on Legendary now, but I saved/quit in the middle of mission Exodus cause it took a while and when I resumed it took me all the way back to the start. It also happened once with a previous mission, which then I completed in one go. So I tried few more times saving at earlier checkpoints, but I always get the same result. EAC is on, iron skull for sure isn’t activated, so no idea what the problem is, it’s intended to be like this? If not… I found some posts from 2014/15 complaining about similar issues and people assumed it was going to be fixed “soon”… by now it’s been 7 years (if we consider also the console version), I don’t wanna believe that they still didn’t fix it? This is throwing me off cause sometimes I really can’t do whole mission in one go, so I hope someone can help about it.

EDIT: now I tried also other missions which previously I saved and it worked perfectly fine, but even there I go back to beginning… same also with other difficulties. I can’t save in the middle of any mission anymore, what’s happening?? :frowning: