"CORE UPDATE, not support saves too outdated and DO NOT OVERWRITE! UNZIP GAME IN A NEW FOLDER!"
Core update means he changed something that has this tendency to break stuf- BUGS FOR THE BUG GOD!!!
I have no idea what versions are too outdated, but I'd still give it a try. To increase your odds keeping your save you can try the following
- Not saving right in the middle of combat (where tons of core stuff happens)
- Make your save on the overmap (leave whatever area you're in)
- Save after doing a rebirth (this will wipe all the dictionaries that keep track of quests and state of the world etc)
Not overwriting the game folder with the updated version means extracting the archive in its own empty folder. You can still delete the old version after successfully updating.