There are no plans to provide further updates for this demo.
Also, you mention you're playing on the web itself, which is not an officially supported way for playing this game. That might explain why you are experiencing bugs with save files.
To properly run the game, you need to download the file on this itchio page, unzip it (right-click on the file and choose "Extract all..."), and then in the extracted folder you can open "Game.exe".