Uhm... something strange happened.
I deleted everything about the game on my computer and downloaded it again and now I was able to play until the end without any problems.
I have no idea why, it just worked.
Viewing post in Sixgun Sally: Back in the Saddle comments
Glad you were able to get it working, even if there’s no real reason why it should or shouldn’t. RPG Maker is basically a bundle of aging Javascript held together with duct tape and prayers, and adding plugins just makes it even more unpredictable, so there are always going to be edge cases or system setups where things don’t always work as intended even if the code I can control looks right.