It's quite a well known bug in here. This is strangely the only area that does this, and I'm guessing they forgot to change a bit of the code to reference the rpgmvo file that is the exact same.
There are two fixes to it: a temp solution and a tested solution that is reliable (until the next update that is.)
Reliable solution:
To fix it, find in the audio folder bgm, and find two files that state "El Infausto Landron de Joyas A.rpgmvo" and "El Infausto Landron de Joyas B.rpgmvo"
You'll want to copy them (just in case of corruption) and change the names respectively to "El Infausto Landron de Joyas A.ogg" and "El Infausto Landron de Joyas B.ogg"
Temp Solution:
You can do what I did first time playing it, which was spam the enter key until I got to the underground section, save the game, and refreshed the game. That also seemed to work as a fix.