Hi chyi33,
Good day,
I've tried to play mp3 music via the Google Play music version 8.18.7847-1L, and it can normal to play in the latest system version WW- v16.0611.1901.1.
I would suggest you update the firmware to the latest for a check.
If this problem still appears, please play another mp3 music for a check and kindly tell me your music player.
Thank you.:)