This is amazingly fun, however, if you are the joining player, the only progress that saves is character progress such as experience and loot. (playstationlifestyle.net)
And there's a neat progression system — instead of traditional levels, characters progress through stat gains that should be familiar to anyone who's played Final Fantasy II; you boost your attack stat by dealing damage, your block stat by taking damage, etc.. (kotaku.com)
A workaround for the issue involved deleting patch 1.01 and playing offline to avoid accidentally auto - updating the game, but this led to issues with saving character progress, and did nothing to fix corrupted game saves. (kotaku.com)