a falta de probarlo creo que he probado la solucion en este post
https://meizufans.eu/forum/topic/235...-mx5/23?page=2
concretamente:
Open the [Security] app and choose [Power Saving], then [App Management] by selecting the App drawer icon at the bottom.
Simply enable the applications you wish to run when the phone is in standby mode. For Google Play music specifically, you need to add this and also the [Google Account Manager] and [Google Play Service] apps or it will not work.
basicamente es permitir que se ejecuten en segundo plano, ademas de google play music, google account manager y google play service
como digo lo tengo que probar