O dear, yep I found the problem.
Gonna fix this tomorrow in the new version (it's 2:12 am here at the moment).
For a quick fix, replace line 39 with @music = Menu_Sounds[rand(Menu_Sounds.size)]
And replace line 53 with @music = Shop_Sounds[rand(Shop_Sounds.size)]
Though a official update tomorrow.
ps. Sorry for the inconvenice, didn't test this version.
A lesson for the next time