Nice to see you revisited and updated the game! Initially I got it when it was 1.x version but I didnt have time to play much, and now I come back and here is 2.0 instead! Cool... and, hey... Happy New Year!
I checked it and rezipped the master version and moved it around between computers and it was still fine. Track 5 was just sitting in there where it's meant to be. You can actually access all the music in the game folder in sounds folder there's a BGM (background music folder) all the WAV files are in there.