I'm having the same problem. It will only display the notification count message (for all apps) while the device is locked. If I unlock it (e.g. using face unlock) while staying on the lock screen the real content is shown. For example I activate the screen -> "1 new notification" -> I move my face in front of the camera -> "Text.. text.. text..". It appears to be some kind of security/privacy feature, but I haven't found a place to turn it off either.