Ditto. My HTC M8 (Sprint 831C) is doing funny things as well with Poweramp on Android 5.0.1. The Poweramp icon stays in the notification bar will not go away unless I reboot the phone. And when I go to the lockscreen, the album art is displayed as the lockscreen wallpaper and no control widget. Just a blank toast notification in the middle of the lockscreen. Music plays fine, just the lockscreen and notification issues.