I’m having what I guess is the same issue. My current save is not loading on the unstable branch, either freezing up during load or right when I get into the game making it unplayable. It’s not an A18 save, I started it this week on the unstable branch so my guess is it’s not the issue linked above by jomaxro.
Here is the link to my save and the logs I gathered for the issue : Dropbox - Stonehearth.zip
The sreenshot in the save is where it froze the one time I managed to load my save.
Please let me know if I can help by providing any more info.