Okay, I'll comb through my code really well again, hop over there, and report back if I find the cause.
I'm going to have to start making commits more often, might lose a few hours of progress to this 😱
EDIT:
OKay, this one was a real turd. I looked through my changes per commit on github, turns out I left the music blank on a map somehow. 'MUS_NONE' is okay, but don't accidentally leave that field blank