it was working but now a different track is messed up,
okay, can you screenshot the error AND the content of the Audio/BGM folder?
This is actually a font problem, believe it or not, I've seen this before, yet I don't know the font to install for it.
Really? I don't know about it at all.
Well, in that case, the default font used is VL Gothic. Pretty sure you can just Google it for the download.
