I got the same problem with the Music player in standby modes. I use the Music player: Poweramp
My older phones has no problem with that app.
When i play music in standby modes the music stopped. I don't give the command to stop the music. He stop the whole app.
The same thing with Live wallpapers from the play Store. I use the live wallpaper Paperland. My older phones have noproblems with that.

Any help will be apprecited.

I didn't find the right solution from the Internet.

Web video animation company

Thank you.