Not sure if this has been submitted or not, but I did the missions Arbiter and Uprising split up between different play sessions. I was able to continue from checkpoints but when finishing the levels, I didn’t get level completion achievements. Also, from the UI it says that they were finished on Heroic but it also doesn’t seem to have counted towards the “beat Halo 2 on Heroic” achievements.
Thanks for the hard work in getting these fixed. It’s great to be playing through the Halo campaigns again!