I see... The save bug and the bug with the door sound very rare, but also very deep rooted bugs. Both calling the save screen and initiating the combat sequence are RPG Maker's own engine commands. I am constantly ironing out the bugs but those sound pretty difficult ones because I haven't messed around with the core engine that much..
The difficulty of the game can seem harsh but there are ways around everything that seems unfair at first. Discord channel and the wiki offer good tips on the game.