pygame.mixer.music approximately 50% of time works

Question

class Music():
  def __init__(self, source):
      self.source = source
      self.clock = pygame.time.Clock()
      self.quit = False
      pygame.mixer.init()
      pygame.display.set_mode((200, 100))
      pygame.mixer.music.load(self.source)
  def play(self):
      pygame.mixer.music.play(0)
      pygame.mixer.music.set_endevent(pygame.USEREVENT)
      self.clock.tick(10)
      while not self.quit:
          try:
              pygame.event.poll()
              self.clock.tick(10)
          except KeyboardInterrupt:
              pygame.mixer.music.stop()
              exit()
music = Music("music.mp3")
music.play()

I'm new to Python. The code will run. However the music sometimes doesn't play.

1st run: Play
2nd run: Play
3rd run: No sound
4th run: No sound
5th run: Play
6th run: Play
7th run: Play
8th run: No sound
9th run: No sound
10th run: Play

Hope you got what I mean, it is not consistent, sometime it works, sometimes don't.
I remember there was one time that when I leave the no sound running, suddenly it got sounds. It's kind of weird.