Music only played through earphones

Hi, I'm making an app and I discover that in one device in particular (iPhone 6S) the music of the game is not beeing played but the sound fx are. But if I connect an earphones, it worked, you can hear the music through the earphones and the sound FX. (The mobile is not muted or anything)

The differences between the music and the sounds are:

Music

• Format: mp3 192kbps
• Loading type: Streaming
  
• Compresion: Vorbis
  
• Quality: 100
  
• Sample rate: Preserve Sample Rate
• They are played as the clip of an audio source and in loop mode

Sound FX

• Format: wav
• Loading type: Decompress on Load
• Compresion: PCM
• Sample Rate: Preserve Sample Rate
• They are played using the PlayOneShot function of an audio source.

On other ios devices, iphone 4, 5, 6 and ipad air it works perfectly.


Any idea about this issue?

Thanks

PS. Could it be an issue with that particular device and not something I did wrong? I dont have more iphone 6s to test, so I don't know

 

Nobody?