Ah, good catch! It's always good when people with uncommon setups try my games, a lot of times it reveals that I'm doing something silly, as was the case this time. I can go ahead and change a certain code comment now, heh.
Thanks for the detailed steps to reproduce the issue! Although, in this case it was a tad unnecessary because the crash was just me calling a method on a source instead of love.audio by mistake.
Not sure if you intend to go back and play more for the secret boss or anything, but if you do know that this crash is fixed on the itch.io release.