The Steam achievements are now working properly after last night's update!
I apologize for the unexpected bugs; that's what happens when you update your engine to a more recent version just before launching a game! Everything seems to be working fine, when boom! Incompatible features strike again!
That said, after another round of thorough testing, it seems there aren't any bugs left in the game, but of course, if you find one don't hesitate to let me know. There's a pinned post in the Community page of the game for that use ;)
Your saved games might not be working due to the change of engine versions: my sincere apology! Remember you can use the "Skip" mode to run the game again until the point you previously were at.