Hi,
Phone: Samsung Galaxy Note 4 with Android 5.1.1. Everything stock. No modifications.
GCM: Always latest version from Google Play.
When I start GCM it occasionally just doesn't start. I can see only a black screen. The interesting part is that notifications (to Fenix 3 in my case) are still working. I can't turn off that black screen (close the app) with back button. The only thing that helps - app force stop. After force stop it starts and works normally.
Have you experienced such GCM behavior?
Thanks!!!