Weird, I'll investigate it! It might be a memory issue. Also, the first save is an autosave, so even if you can't manually save for some reason, it should still autosave your progress, as long as you don't overwrite it by going to another save
It wouldn't even autosave for a while, I went to every location and nothing happened, I noticed saving stops working when you get up to UNA, at least for me, IDK if its the same for anyone else.
I've checked and there's nothing preventing my pc from preventing the game to write files, I've just taken to waiting a few minutes and then usually it lets me save
