https://www.reddit.com/r/xbox/comments/1ljc7r2/ama_with_the_creators_of_the_alters_from_11_bit/?sort=new
"The good news is that the CE-100028-1 save error has already been identified and fixed in hotfix 1.0.2, which recently went live. It should be available on PS5 very soon, so we just ask for a little more patience.
Once the update hits your platform, the save issue should no longer occur. Fingers crossed you’ll be able to continue without losing any progress!"