Thanks for the details! This is the error mentioned under "Troubleshooting" in the dev log post. It's the game not recognizing newly added choice flags and invalidating that particular save. The only way I know to fix it is to start a new game and skip forward to the point you left off. It's a pain, but unfortunately happens since this is an in-development game. Skipping through usually only takes a minute or two, thankfully, you'll just need to click your choices again.