Edit: We're happy to share that we addressed the glitch affecting the 13th boss fight on Windows now.
Thanks so much for playing! We're really sorry if you ran into any bugs. It looks like the 13th boss had an issue on Windows, but we're on it and will fix it as soon as possible. In the meantime, remember to save your progress and use the pause menu to skip through stages.
As for the audio effect, that's intentional—the character cut off your earlobes, so you're a bit deaf now! But if it’s not your thing, you can turn it off in the pause menu too.